* 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

Properly follow ternary else() chain, help out by pre-pending if()
Resolve #2239, thanks to @sigmafx

- 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

https://github.com/xoseperez/espurna/pull/1772#issuecomment-609847420
> Without the patch btnRepDel overrides every btnRepDel0, btnRepDel1 etc., btnRepDel0 read second, then hard-coded value.
With the patch btnRepDel0 is read first, then btnRepDel, then hard-coded value.

Indexed key can only be set via settings upload or in terminal, WebUI can change only the global override setting. Allow more 'specific' key to override global setting.

* mqtt: enum state

* mqtt: async client buffer with MQTT_MAX_PACKET_SIZE

* mqtt: rework debug messages

* mqtt: MQTT_BUFFER_MAX_SIZE

* mqtt/test: debug log for async callback

* mqtt/test: don't log things we don't handle

* button: fix typo

In case board configuration is empty, loop should try to check at least once

* wip

* cleanup buttons-through-serial code, remove hw mention from button module

* remove wip

* implement mqtt settings

* fixup struct members, dual no longer allocates debouncer

* add missing debounceevent lib

* fix missing event_handler, update names

* fix namespace

* drop lib

* fix int<->bool comparison

* Move gpio16 handling from DigitalPin to EventHandler

* Cleanup debounceevent headers

* Don't expect system headers to be included

* re 70b54c489f - no allocation, for real

* Adjust settings names

* dont retain by default

* unused

* typo

* Fix length type (ref 6017ad9474)

* Move pin class outside of debounce lib, lowercase ns

* move event handling inside of button_t

* refactor config. ..._MODE -> _CONFIG, ..._MODE_... -> ..._ACTION_...

* fix test

* naming

* move indexed value to header

* refactor actions into direct opts

* fix webui, fix buttons not respecting old user setting

* change button config format from bitmask to a struct, adjust settings conversion

* proxy some more header defautls, fix web kv

* gpiopin

* adjust webui func to support every setting

* clarify single-return event->string

* fix dual setting

* fix dual packet condition, de-duplicate funcs

* fix bogus warning

* Fixes and updates for thermostat and display:

- Switch to original esp8266-oled-ssd1306 library
- Fixes and updates for thermostat and display
- Add display switching off after interval
- If THERMOSTAT_DISPLAY_SUPPORT enabled, then one click enable display, long click switch relay. This functionality also depend on fix for long click. See pull request https://github.com/xoseperez/espurna/pull/2172

* Move buttons definitions for display to dependencies.h

* Pin ThingPulse/esp8266-oled-ssd1306#3398c97

- use similar to relay & wifi, configuration through helper methods that
  use indexed defines
- clock cycles for led delay polling
- button mode defaults

* 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

- mask is defined as (relay# status << number)
- transparently handle base-2 and base-10 numbers
- if the relay mode requires us to save the mask, it will be saved as base-2

- 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