- 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

* Core 2.6.0+ fixes

* fix env -> config, run travis04 job

* don't duplicate free heap in frag data, use single stats struct

* fix dtostrf warnings, bump buffer sizes

* ...and even less words for fragmentation stat

* relays: locked status

* remove debug

* Disable relay toggle when locked

* fixup! Disable relay toggle when locked

* Send lock with status, fix "disable" condition

* typo

* Update WebUI

- 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

* send all ws config at once on start
* reduce ws json overhead by creating message buffer manually
* use k:[values] instead of k1:value1, k2:value2 etc. for lists

This reverts commit 7ad0e3a02b.

Add button definitions to the travis02 and travis03
IR_BUTTON should be uint32_t to properly work with new macro
eepromRotate return value is not used