Change light definitions, add support for PAR8.

Previously we had RGB+Fade, but the lights we happen to have are what I
will call PAR8, in that they use 8 DMX channels and include support for
various functions as well as RGB.

Change 'white' to 'single', and a few other cleanups.
Update zone backgrounds on change.

This requires a rather ugly change to output the entire lighting status
on each emit, but I'll choose functionality over correctness for now and
tidy up later.

Still to do: update zones on preset change.
Update zone colour on preset change.

This has complete disregard for the possibility of individual LED
changes within a zone, as well as for zones which start with a single
LED.  Basically it is a really ugly hack for some functionality I need
at the moment..