resolve #2310

- introduce zero threshold setting to reset value to 0 below a certain point (resolve #2264)
for example, set pwrPZeroThreshold0 10.0 for active power (or pwrQ... for apparent, pwrModS... for reactive) will reset always reset value to 0, similar to what turned off relay does. Default value is nan, since we can't use 0.0 on account of negative values.
- fix energy magnitude indexes usage, properly reset in API
- simplify sending pwr and emon Visible flags
- allow to use settings prefixes more, remove snsMinDelta & snsMaxDelta and use relative magnitude indexes

* wip based on early draft. todo benchmarking

* fixup eraser, assume keys are unique

* fix cursor copy, test removal at random

* small benchmark via permutations. todo lambdas and novirtual

* fix empty condition / reset

* overwrite optimizations, fix move offsets overflows

* ...erase using 0xff instead of 0

* test the theory with code, different length kv were bugged

* try to check for out-of-bounds writes / reads

* style

* trying to fix mover again

* clarify length, defend against reading len on edge

* fix uncommited rewind change

* prove space assumptions

* more concise traces, fix move condition (agrh!!!)

* slightly more internal knowledge (estimates API?)

* make sure cursor is only valid within the range

* ensure 0 does not blow things

* go back up

* cursor comments

* comments

* rewrite writes through cursor

* in del too

* estimate kv storage requirements, return available size

* move raw erase / move into a method, allow ::set to avoid scanning storage twice

* refactor naming, use in code

* amend storage slicing test

* fix crash handler offsets, cleanup configuration

* start -> begin

* eeprom readiness

* dependencies

* unused

* SPI_FLASH constants for older Core

* vtables -> templates

* less include dependencies

* gcov help, move estimate outside of the class

* writer position can never match, use begin + offset

* tweak save_crash to trigger only once in a serious crash

* doh, header function should be inline

* foreach api, tweak structs for public api

* use test helper class

* when not using foreach, move cursor reset closer to the loop using read_kv

* coverage comments, fix typo in tests decltype

* ensure set() does not break with offset

* make codacy happy again

Change the underlying command line handling:
- switch to a custom parser, inspired by redis / sds
- update terminalRegisterCommand signature, pass only bare minimum
- clean-up `help` & `commands`. update settings `set`, `get` and `del`
- allow our custom test suite to run command-line tests
- clean-up Stream IO to allow us to print large things into debug stream (for example, `eeprom.dump`)
- send parsing errors to the debug log

As a proof of concept, introduce `TERMINAL_MQTT_SUPPORT` and `TERMINAL_WEB_API_SUPPORT`
- MQTT subscribes to the `<root>/cmd/set` and sends response to the `<root>/cmd`. We can't output too much, as we don't have any large-send API.
- Web API listens to the `/api/cmd?apikey=...&line=...` (or PUT, params inside the body). This one is intended as a possible replacement of the `API_SUPPORT`. Internals introduce a 'task' around the AsyncWebServerRequest object that will simulate what WiFiClient does and push data into it continuously, switching between CONT and SYS.

Both are experimental. We only accept a single command and not every command is updated to use Print `ctx.output` object. We are also somewhat limited by the Print / Stream overall, perhaps I am overestimating the usefulness of Arduino compatibility to such an extent :)
Web API handler can also sometimes show only part of the result, whenever the command tries to yield() by itself waiting for something. Perhaps we would need to create a custom request handler for that specific use-case.

- compat.h right after config
- remove broker.h from global header
- add 'hint' about eeprom methods into settings

* broker: declare and define per module

We no longer need to specify each Broker type in broker.h
But, we exchange that bit for explicit initialization of the instance

Define helper macros to generate boilerplate code
- namespace with Instance, Register(), Publish()
- forward Register(...) -> Instance.Register(...),
  Publish(...) -> Instance.Publish(...)

* don't check for broker when deps enable it

* emon: configure ratios without reboot

* settings: serialize() support

* debug: use vsnprintf from newlib, not from sdk

* settings/experimental: show defaults via `get`

* emon: override base methods, fix defaults

* sensor/emon: expose internal index calculation

- refactor configuration to use the correct index when accessing indexed
  sensor methods. store index value on magnitude, refactor loops to
  accomodate this new functionality
- rename slot(index) -> description(index), since we use 'slot' as
  numeric value

- general conversion from .ino modules into a separate .cpp files
- clean-up internal headers, place libraries into .h. guard .cpp with _SUPPORT flags 
- fix some instances of shared variables instead of public methods
- tweak build system to still build a single source file via os environment variable ESPURNA_BUILD_SINGLE_SOURCE

* Config: remove prototypes.h

* fixup order

* word

* add missing

* fix warning while still using .ino

* bad at c/p;

* experimental: refactor get/set/del/hasSetting

* sensors

* lights

* cleaup

* r

* tuya

* fixup! sensors

* fixup! tuya

* header defaults types

* fix lights

* setup already checks for max

* helper for flashstring

* fix overload

* oops

* refactor includes

* warnings

* test with migrate

* add ids in a separate file

* cleanup

rev: crash

rev: domoticz

rev: encoder

rev: loopdelay

rev: hass

rev: i2c

rev2: hass

rev: mqtt

rev: rfm69

rev: relay

rev: rpn

rev: settings setup

rev: hb settings

rev: telnet preprocessor fix

rev: settings wrap

rev: tspk bool style

rev: wifi types

rev: util hb

rev: settings

fixup! rev: settings

* rev: cleanup wifi injections based on new getters

* hasSetting now can return true for empty key

* show hardcoded network in web

* oops

* fix ws referencing wrong index

* ensure empty strings are written

* c/p

* use experimental schema style for payload, mark network as not deletable

* allow to customize converter

* shorter syntax, try using with wifi

* use proper #if syntax to handle definitions that are missing

* fixup ota sc checks getter, cast schEnabled to bool

* add utils header to sensors

- remove "platform" key, see #1440. this implicitly sets schema to "basic". pending some other clean-up regarding json and mqtt queueing, other schema can be added down the line 
- updated ws module queue elem to capture callbacks list, allows to pass more than one callback (for example, when they are generated on the fly as lambdas, see ha wsPost usage)
- modified method to send ha config to use global ws queue, fix #1762 problem with empty topics and ensure json allocation is consistent.
- use existing defines to set mqtt payload options. amend #1085, #1188, #1883 to use the set payload value. drop HOMEASSISTANT_PAYLOAD... defines. 
- update MQTT_STATUS_ONLINE/OFFLINE and RELAY_MQTT_ON/OFF with runtime configuration
- filter payload strings so that the resulting yaml value is not interpreted as bool (python True, False)
- helper method for settings to streamline string values manipulation

- update every dynamicjsonbuffer with fixed size constructor argument
- change to ws callback registration to use a class builder (just cosmetic)
- test multiple ws data callbacks for each module
- remove some of the static strings in favour of ws data callback
- improve sensor ws callback data size, remove duplicated strings
- use static buffer in wsDebugSend
- postpone wsSend until loop, implement wsPost to allow other modules to queue message callbacks. remove Ticker based ws callbacks for data
- update WebUI files

- store system crash counter and reset reason in rtcmem instead of eeprom
- store relay state mask in rtc in addition to the eeprom
- store relay state in eeprom only when boot mode requires it
- simplify relay state mask calculation / reading using std::bitset
- light state save and restore
- energy total save and restore

* PZEM004T: runtime port and address settings

* Add nodemcu-pzem004t test env

* pzEneTotal -> pzemEneTotal

This is the Info main menu (aka directory node).
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Basics
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* Coreutils: (coreutils).       Core GNU (file, text, shell) utilities.
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C++ libraries
* autosprintf: (autosprintf).   Support for printf format strings in C++.

Compression
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Development
* SSIP: (ssip).                 Speech Synthesis Interface Protocol.
* Speech Dispatcher: (speech-dispatcher).
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DOS
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Editors
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General Commands
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GNU Gettext Utilities
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* msginit: (gettext)msginit Invocation.
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* msgmerge: (gettext)msgmerge Invocation.
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GNU organization
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GNU Utilities
* dirmngr-client: (gnupg).      X.509 CRL and OCSP client.
* dirmngr: (gnupg).             X.509 CRL and OCSP server.
* gpg: (gnupg1).                OpenPGP encryption and signing tool (v1).
* gpg-agent: (gnupg).           The secret key daemon.
* gpg2: (gnupg).                OpenPGP encryption and signing tool.
* gpgsm: (gnupg).               S/MIME encryption and signing tool.

Individual utilities
* aclocal-invocation: (automake-1.15)aclocal Invocation.
                                                Generating aclocal.m4.
* arch: (coreutils)arch invocation.             Print machine hardware name.
* automake-invocation: (automake-1.15)automake Invocation.
                                                Generating Makefile.in.
* base32: (coreutils)base32 invocation.         Base32 encode/decode data.
* base64: (coreutils)base64 invocation.         Base64 encode/decode data.
* basename: (coreutils)basename invocation.     Strip directory and suffix.
* bibtex: (web2c)bibtex invocation.             Maintaining bibliographies.
* cat: (coreutils)cat invocation.               Concatenate and write files.
* chcon: (coreutils)chcon invocation.           Change SELinux CTX of files.
* chgrp: (coreutils)chgrp invocation.           Change file groups.
* chmod: (coreutils)chmod invocation.           Change access permissions.
* chown: (coreutils)chown invocation.           Change file owners and groups.
* chroot: (coreutils)chroot invocation.         Specify the root directory.
* cksum: (coreutils)cksum invocation.           Print POSIX CRC checksum.
* cmp: (diffutils)Invoking cmp.                 Compare 2 files byte by byte.
* comm: (coreutils)comm invocation.             Compare sorted files by line.
* cp: (coreutils)cp invocation.                 Copy files.
* csplit: (coreutils)csplit invocation.         Split by context.
* cut: (coreutils)cut invocation.               Print selected parts of lines.
* date: (coreutils)date invocation.             Print/set system date and time.
* dd: (coreutils)dd invocation.                 Copy and convert a file.
* df: (coreutils)df invocation.                 Report file system disk usage.
* diff: (diffutils)Invoking diff.               Compare 2 files line by line.
* diff3: (diffutils)Invoking diff3.             Compare 3 files line by line.
* dir: (coreutils)dir invocation.               List directories briefly.
* dircolors: (coreutils)dircolors invocation.   Color setup for ls.
* dirname: (coreutils)dirname invocation.       Strip last file name component.
* du: (coreutils)du invocation.                 Report on disk usage.
* dvicopy: (web2c)dvicopy invocation.           Virtual font expansion
* dvitomp: (web2c)dvitomp invocation.           DVI to MPX (MetaPost pictures).
* dvitype: (web2c)dvitype invocation.           DVI to human-readable text.
* echo: (coreutils)echo invocation.             Print a line of text.
* env: (coreutils)env invocation.               Modify the environment.
* expand: (coreutils)expand invocation.         Convert tabs to spaces.
* expr: (coreutils)expr invocation.             Evaluate expressions.
* factor: (coreutils)factor invocation.         Print prime factors
* false: (coreutils)false invocation.           Do nothing, unsuccessfully.
* find: (find)Invoking find.                    Finding and acting on files.
* fmt: (coreutils)fmt invocation.               Reformat paragraph text.
* fold: (coreutils)fold invocation.             Wrap long input lines.
* gftodvi: (web2c)gftodvi invocation.           Generic font proofsheets.
* gftopk: (web2c)gftopk invocation.             Generic to packed fonts.
* gftype: (web2c)gftype invocation.             GF to human-readable text.
* groups: (coreutils)groups invocation.         Print group names a user is in.
* gunzip: (gzip)Overview.                       Decompression.
* gzexe: (gzip)Overview.                        Compress executables.
* head: (coreutils)head invocation.             Output the first part of files.
* hostid: (coreutils)hostid invocation.         Print numeric host identifier.
* hostname: (coreutils)hostname invocation.     Print or set system name.
* id: (coreutils)id invocation.                 Print user identity.
* install: (coreutils)install invocation.       Copy files and set attributes.
* join: (coreutils)join invocation.             Join lines on a common field.
* kill: (coreutils)kill invocation.             Send a signal to processes.
* link: (coreutils)link invocation.             Make hard links between files.
* ln: (coreutils)ln invocation.                 Make links between files.
* locate: (find)Invoking locate.                Finding files in a database.
* logname: (coreutils)logname invocation.       Print current login name.
* ls: (coreutils)ls invocation.                 List directory contents.
* md5sum: (coreutils)md5sum invocation.         Print or check MD5 digests.
* mf: (web2c)mf invocation.                     Creating typeface families.
* mft: (web2c)mft invocation.                   Prettyprinting Metafont source.
* mkdir: (coreutils)mkdir invocation.           Create directories.
* mkfifo: (coreutils)mkfifo invocation.         Create FIFOs (named pipes).
* mknod: (coreutils)mknod invocation.           Create special files.
* mktemp: (coreutils)mktemp invocation.         Create temporary files.
* mltex: (web2c)MLTeX.                          Multi-lingual TeX.
* mpost: (web2c)mpost invocation.               Creating technical diagrams.
* mv: (coreutils)mv invocation.                 Rename files.
* nice: (coreutils)nice invocation.             Modify niceness.
* nl: (coreutils)nl invocation.                 Number lines and write files.
* nohup: (coreutils)nohup invocation.           Immunize to hangups.
* nproc: (coreutils)nproc invocation.           Print the number of processors.
* numfmt: (coreutils)numfmt invocation.         Reformat numbers.
* od: (coreutils)od invocation.                 Dump files in octal, etc.
* paste: (coreutils)paste invocation.           Merge lines of files.
* patch: (diffutils)Invoking patch.             Apply a patch to a file.
* patgen: (web2c)patgen invocation.             Creating hyphenation patterns.
* pathchk: (coreutils)pathchk invocation.       Check file name portability.
* pktogf: (web2c)pktogf invocation.             Packed to generic fonts.
* pktype: (web2c)pktype invocation.             PK to human-readable text.
* pltotf: (web2c)pltotf invocation.             Property list to TFM.
* pooltype: (web2c)pooltype invocation.         Display WEB pool files.
* pr: (coreutils)pr invocation.                 Paginate or columnate files.
* printenv: (coreutils)printenv invocation.     Print environment variables.
* printf: (coreutils)printf invocation.         Format and print data.
* ptx: (coreutils)ptx invocation.               Produce permuted indexes.
* pwd: (coreutils)pwd invocation.               Print working directory.
* readlink: (coreutils)readlink invocation.     Print referent of a symlink.
* realpath: (coreutils)realpath invocation.     Print resolved file names.
* rm: (coreutils)rm invocation.                 Remove files.
* rmdir: (coreutils)rmdir invocation.           Remove empty directories.
* runcon: (coreutils)runcon invocation.         Run in specified SELinux CTX.
* sdiff: (diffutils)Invoking sdiff.             Merge 2 files side-by-side.
* seq: (coreutils)seq invocation.               Print numeric sequences
* sha1sum: (coreutils)sha1sum invocation.       Print or check SHA-1 digests.
* sha2: (coreutils)sha2 utilities.              Print or check SHA-2 digests.
* shred: (coreutils)shred invocation.           Remove files more securely.
* shuf: (coreutils)shuf invocation.             Shuffling text files.
* sleep: (coreutils)sleep invocation.           Delay for a specified time.
* sort: (coreutils)sort invocation.             Sort text files.
* split: (coreutils)split invocation.           Split into pieces.
* stat: (coreutils)stat invocation.             Report file(system) status.
* stdbuf: (coreutils)stdbuf invocation.         Modify stdio buffering.
* stty: (coreutils)stty invocation.             Print/change terminal settings.
* sum: (coreutils)sum invocation.               Print traditional checksum.
* sync: (coreutils)sync invocation.             Synchronize memory to disk.
* tac: (coreutils)tac invocation.               Reverse files.
* tail: (coreutils)tail invocation.             Output the last part of files.
* tangle: (web2c)tangle invocation.             WEB to Pascal.
* tee: (coreutils)tee invocation.               Redirect to multiple files.
* test: (coreutils)test invocation.             File/string tests.
* tex: (web2c)tex invocation.                   Typesetting.
* tftopl: (web2c)tftopl invocation.             TFM -> property list.
* time: (time).                                 Run programs and summarize
                                                  system resource usage.
* timeout: (coreutils)timeout invocation.       Run with time limit.
* touch: (coreutils)touch invocation.           Change file timestamps.
* tr: (coreutils)tr invocation.                 Translate characters.
* true: (coreutils)true invocation.             Do nothing, successfully.
* truncate: (coreutils)truncate invocation.     Shrink/extend size of a file.
* tsort: (coreutils)tsort invocation.           Topological sort.
* tty: (coreutils)tty invocation.               Print terminal name.
* uname: (coreutils)uname invocation.           Print system information.
* unexpand: (coreutils)unexpand invocation.     Convert spaces to tabs.
* uniq: (coreutils)uniq invocation.             Uniquify files.
* unlink: (coreutils)unlink invocation.         Removal via unlink(2).
* updatedb: (find)Invoking updatedb.            Building the locate database.
* uptime: (coreutils)uptime invocation.         Print uptime and load.
* users: (coreutils)users invocation.           Print current user names.
* vdir: (coreutils)vdir invocation.             List directories verbosely.
* vftovp: (web2c)vftovp invocation.             Virtual font -> virtual pl.
* vptovf: (web2c)vptovf invocation.             Virtual pl -> virtual font.
* wc: (coreutils)wc invocation.                 Line, word, and byte counts.
* weave: (web2c)weave invocation.               WEB to TeX.
* who: (coreutils)who invocation.               Print who is logged in.
* whoami: (coreutils)whoami invocation.         Print effective user ID.
* xargs: (find)Invoking xargs.                  Operating on many files.
* yes: (coreutils)yes invocation.               Print a string indefinitely.
* zcat: (gzip)Overview.                         Decompression to stdout.
* zdiff: (gzip)Overview.                        Compare compressed files.
* zforce: (gzip)Overview.                       Force .gz extension on files.
* zgrep: (gzip)Overview.                        Search compressed files.
* zmore: (gzip)Overview.                        Decompression output by pages.

Kernel
* GRUB: (grub).                 The GRand Unified Bootloader
* grub-dev: (grub-dev).         The GRand Unified Bootloader Dev
* grub-install: (grub)Invoking grub-install.
                                Install GRUB on your drive
* grub-mkconfig: (grub)Invoking grub-mkconfig.
                                Generate GRUB configuration
* grub-mkpasswd-pbkdf2: (grub)Invoking grub-mkpasswd-pbkdf2.
* grub-mkrelpath: (grub)Invoking grub-mkrelpath.
* grub-mkrescue: (grub)Invoking grub-mkrescue.
                                Make a GRUB rescue image
* grub-mount: (grub)Invoking grub-mount.
                                Mount a file system using GRUB
* grub-probe: (grub)Invoking grub-probe.
                                Probe device information
* grub-script-check: (grub)Invoking grub-script-check.

Libraries
* RLuserman: (rluserman).       The GNU readline library User's Manual.

Man-pages
* Latex2man: (latex2man).       Its Man-Page

Math
* bc: (bc).                     An arbitrary precision calculator language.
* dc: (dc).                     Arbitrary precision RPN "Desktop Calculator".

Network applications
* Wget: (wget).                 Non-interactive network downloader.

Programming
* flex: (flex).                 Fast lexical analyzer generator (lex
                                  replacement).
* gnucash: (gnucash-design).    Design of the GnuCash program

Programming Tools
* Gperf: (gperf).               Perfect Hash Function Generator.

Software development
* Autoconf Archive: (autoconf-archive).
                                A collection of re-usable Autoconf macros.
* Automake: (automake-1.15).    Making GNU standards-compliant Makefiles.

Sound
* SSIP: (ssip).                 Speech Synthesis Interface Protocol.
* Say for Speech Dispatcher: (spd-say).
                                Say.
* Speech Dispatcher: (speech-dispatcher).
                                Speech Dispatcher.

TeX
* DVI-to-PNG: (dvipng).         Translating TeX DVI files to Portable Network
                                  Graphics (PNG).
* DVI-to-Postscript: (dvips).   Translating TeX DVI files to PostScript.
* Eplain: (eplain).             Expanding on plain Tex.
* EpsPDF: (epspdf).             Portable GUI- and command-line EPS/PS/PDF
                                  conversion
* Kpathsea: (kpathsea).         File lookup along search paths.
* LaTeX2e: (latex2e).           Unofficial LaTeX reference manual.
* LaTeX2e-es: (latex2e-es).     Manual de extraoficial de LaTeX.
* Naming TeX fonts: (fontname). Filenames for TeX fonts.
* TL-build: (tlbuild).          TeX Live configuration and development.
* TeX Directories: (tds).       A directory structure for TeX files.
* TeXdraw: (texdraw).           A system for producing PostScript drawings
                                  from TeX.
* Web2c: (web2c).               TeX, Metafont, and companion programs.
* afm2tfm: (dvips)Invoking afm2tfm.
                                Making Type 1 fonts available to TeX.
* dvipng: (dvipng).             A DVI-to-PNG translator.
* dvips: (dvips)Invoking Dvips. DVI-to-PostScript translator.
* kpsewhich: (kpathsea)Invoking kpsewhich.
                                TeX file searching.
* mf2pt1: (mf2pt1).             PostScript Type 1 fonts from Metafont source.
* mktexfmt: (kpathsea)mktex scripts.
                                Format (fmt/base/mem) generation.
* mktexlsr: (kpathsea)Filename database.
                                Update ls-R.
* mktexmf: (kpathsea)mktex scripts.
                                MF source generation.
* mktexpk: (kpathsea)mktex scripts.
                                PK bitmap generation.
* mktextex: (kpathsea)mktex scripts.
                                TeX source generation.
* mktextfm: (kpathsea)mktex scripts.
                                TeX font metric generation.

Text creation and manipulation
* Diffutils: (diffutils).       Comparing and merging files.
* M4: (m4).                     A powerful macro processor.
* grep: (grep).                 Print lines matching a pattern.
* sed: (sed).                   Stream EDitor.   command. Use *  SSID  MODE  CHAN  RATE  SIGNAL  BARS  SECURITY  to get current connections