Started refactor to use UDP-only (for firmware v1.2) and simplify things a little
Implemented on and off, and per-bulb commands
More useful utility commands
Updated MQTT bridge to use newer interface
Merge branch 'fw12'

This is to make the code compatible with the v1.2 firmware which seems
to do everything over UDP.  It simplifies the data structures, but that
means that some of the emitted data uses slightly different field names
so will break any pre-existing code.