Split lights into classes

[jnimmo]

Our if statements are getting too long! Need to split them out into subclasses for each different fixture.

[bartfeenstra]

Would it be an idea to allow light device configuration to specify a channel layout? I need RGBD, for instance, and I can imagine other users have lights that require yet again different layouts. Each channel could then receive a type indicator, and a modifier, such as r,g,b,d (RGB + dimmer), r,g,b,w (RGB + white value), and r,g,b,wa (RGB + auto white value).