Display class gets access to App interface and HmRadio
Display class prepares relevant online information for displays in new DisplayData structure
Displays get pointer to DisplayData and only use information received from there
improved saving settings of display #747, #746
disabled contrast for Nokia display #746
added Prometheus as compile option #719, #615
update MQTT lib to v1.4.1
limit decimal places to 2 in `live`
added `-DPIO_FRAMEWORK_ARDUINO_MMU_CACHE16_IRAM48` to esp8266 debug build #657
a `max-module-power` of `0` disables channel in live view `setup`