* Made rf2 sending and receiving work
With code from https://github.com/1technophile/OpenMQTTGateway/pull/109
plus some other fixes.
* Added support for group bit
Added support for sending and receiving group bit
* Group bit and MQTT retransmitting
Added support for sending and receiving group bit.
Made the gateway transmit the new state of a RF2 switch to the MQTT state topic when it receives a MQTT command to control that switch.
* Removed hard coded RF2 code length
* Added support for dimming to RF2
Verified to work with Nexa WMR-250 dimmer.
* Minor cleanup
Lars Englund