Home Assistant updates

[mcspr]

• remove "platform" key, see Depreciated warnings from home-assistant #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 show config topic field blank when code uploaded from platformio #1762 problem with empty topics and ensure json allocation is consistent.
• use existing defines to set mqtt payload options. amend Support publishing custom value for relay processing #1085, Define HOMEASSISTANT_PAYLOAD_AVAILABLE for payload_available #1188 to use the set payload value. drop HOMEASSISTANT_PAYLOAD... defines. fixes MQTT relay payload ON / OFF inconsistent usage #1883
• update MQTT_STATUS_ONLINE/OFFLINE and RELAY_MQTT_ON/OFF with runtime configuration
• filter payload strings so that resulting yaml value is not interpreted as bool
• helper method for settings to streamline string values manipulation

[mcspr]

• use existing defines to set mqtt payload options. amend Support publishing custom value for relay processing #1085, Define HOMEASSISTANT_PAYLOAD_AVAILABLE for payload_available #1188 to use the set payload value. drop HOMEASSISTANT_PAYLOAD... defines. fixes MQTT relay payload ON / OFF inconsistent usage #1883
• update MQTT_STATUS_ONLINE/OFFLINE and RELAY_MQTT_ON/OFF with runtime configuration

cc @Yonsm, as that was the latest change to the status payload string. now, only one define needs to be specified