Add support for Rotary Encoder sensor

[user2684]

See #310

[user2684]

Need hw to test this out and probably is pointless if not combined with other sensors like e.g. a dimmable led.
Example: https://github.com/mysensors/MySensorsArduinoExamples/blob/master/examples/DimmableLightWithRotaryEncoderButton/DimmableLightWithRotaryEncoderButton.ino
Postponing.