see 69c65a6a40 (commitcomment-42008295)
Because of the way DHCP is integrated into the Core logic, we need to
call wifi_softap_add_dhcps_lease(...) inbetween WiFi.softApConfig(...) and WiFi.softAp(...)

Remember MAC for the current IP sequence number
(e.g. lease 0 -> xxx.xxx.xxx.2, lease 1 -> xxx.xxx.xxx.3 and etc.)

~500 bytes of code

- replace `apmode` with `wifiApMode`
- deprecate `WIFI_FALLBACK_APMODE` in favour of the AP mode setting
- allow to set custom SSID and passphrase for the softAP via `wifiApSsid` & `wifiApPass`
- identifier fallback for hostname

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.

* 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

* 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

* Test: check core feature build

* order

* add missing

* web: re-add wifi scan action, send as json array

* ws: forcibly inline send functions

* use indexed getsetting
* store defaults in progmem

* test: etharp_gratuitous

* proper checks before calling etharp_gratuitous, move includes

* disable at runtime

* ms values

* reload

* debug

* reword

* filter by ifnum instead of checking for AP mode

* drop station_if check

2.3.0/lwip1 builds netif->num increments on for each sta or ap
lwip2 keeps those constant, but that seems like a implementation detail
might break in the future anyways...

* Stop updating SoftAP SSID and password when changing hostname and password via WebUI / settings `reload`:
https://gitter.im/tinkerman-cat/espurna?at=5d65418f49ac051923be1f06
* Show real ssid and psk values from the current sdk configuration instead of using getSetting
* `WIFI.STA` command

- 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

* Make compilation more flexible allowing to define in custom.h your own variation to devices and define four wifi networks

* Implement suggestion from Max Prokhorov, it's simpler and cleaner

* Change a #elif by #else

* Move ESPurna Core comment

This reverts commit 7ad0e3a02b.

This is the Info main menu (aka directory node).
A few useful Info commands:

  'q' quits;
  '?' lists all Info commands;
  'h' starts the Info tutorial;
  'mTexinfo RET' visits the Texinfo manual, etc.

* Menu:

Basics
* Common options: (coreutils)Common options.
* Coreutils: (coreutils).       Core GNU (file, text, shell) utilities.
* Date input formats: (coreutils)Date input formats.
* Ed: (ed).                     The GNU line editor
* File permissions: (coreutils)File permissions.
                                Access modes.
* Finding files: (find).        Operating on files matching certain criteria.

C++ libraries
* autosprintf: (autosprintf).   Support for printf format strings in C++.

Compression
* Gzip: (gzip).                 General (de)compression of files (lzw).

Development
* SSIP: (ssip).                 Speech Synthesis Interface Protocol.
* Speech Dispatcher: (speech-dispatcher).
                                Speech Dispatcher.
* libffi: (libffi).             Portable foreign-function interface library.

DOS
* Mtools: (mtools).             Mtools: utilities to access DOS disks in Unix.

Editors
* nano: (nano).                 Small and friendly text editor.

General Commands
* Screen: (screen).             Full-screen window manager.

GNU Gettext Utilities
* autopoint: (gettext)autopoint Invocation.
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* envsubst: (gettext)envsubst Invocation.
                                Expand environment variables.
* gettextize: (gettext)gettextize Invocation.
                                Prepare a package for gettext.
* gettext: (gettext).           GNU gettext utilities.
* ISO3166: (gettext)Country Codes.
                                ISO 3166 country codes.
* ISO639: (gettext)Language Codes.
                                ISO 639 language codes.
* msgattrib: (gettext)msgattrib Invocation.
                                Select part of a PO file.
* msgcat: (gettext)msgcat Invocation.
                                Combine several PO files.
* msgcmp: (gettext)msgcmp Invocation.
                                Compare a PO file and template.
* msgcomm: (gettext)msgcomm Invocation.
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* msgconv: (gettext)msgconv Invocation.
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* msgen: (gettext)msgen Invocation.
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* msgexec: (gettext)msgexec Invocation.
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* msgfilter: (gettext)msgfilter Invocation.
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* msgfmt: (gettext)msgfmt Invocation.
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* msggrep: (gettext)msggrep Invocation.
                                Select part of a PO file.
* msginit: (gettext)msginit Invocation.
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* msgmerge: (gettext)msgmerge Invocation.
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* msgunfmt: (gettext)msgunfmt Invocation.
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* msguniq: (gettext)msguniq Invocation.
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* xgettext: (gettext)xgettext Invocation.
                                Extract strings into a PO file.

GNU organization
* Maintaining Findutils: (find-maint).
                                Maintaining GNU findutils

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