- stack-like discovery struct to store pending mqtt topic and
message
- use separate json objects for sensor and switch data (different solution for the #1957)

- customize relay TOGGLE payload
- match payload string when receiving mqtt status message
- reference enum values instead of raw integers, spell out intended status
- remove dead code

amend #1885, capitalize `relayPayload...` suffix instead of using uppercase
add `relayPayloadToggle`

- 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

* add CCT support for 2 channel boards

* update webinterface description

* add 2 channel CCT to homeassistant and domoticz

* remove domoticz two channel cct support.

* MQTT and HA brightness shall only be depended on LIGHT_PROVIDER != LIGHT_PROVIDER_NONE

* remove unnecessary changes

This reverts commit 7ad0e3a02b.

This reverts commit f01f2454cc.

Closes #849