New apiRegister depends on `webServer()` returning a valid object.

- RF_... -> RFB_...
- rework rcswitch integration, support variable length payload
- rework rfbridge parser (not tested)
- rework settings scanning routine when trying to match rf payload
  with the relay ID
- update build tests

* 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

- 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

- 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

* Update crash handler

- limit recorder stack size by 128 bytes
- offset settings a bit more
- add possibility to disable crash crash recoder completely

* nicer setting names, comment layout change

- 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

- remove optional RFRAW_SUPPORT
- enable module when RF_SUPPORT=1, optionally enable RCSwitch
- reorder ifdef checks to treat RFB_DIRECT and old RF_SUPPORT the same
- rename RF_PIN to RFB_RX_PIN
- depend on RF_SUPPORT instead of ITEAD_SONOFF_RFBRIDGE
- runtime TX & RX PIN setting

* Call delay() after callbacks
* Use safer loop delay value

- Heartbeat mode and interval configuration added to WebUI ADMIN page
- New option HEARTBEAT_REPEAT_STATUS: on device startup full heartbeat information and after HEARTBEAT_INTERVAL only STATUS report.
- Enhanced first heartbeat message - on device startup it will send heartbeat after ntpSynced will be true to get device time.

P.S. Code is tested. Web part is not compiled, and not tested. I hope it will work :)