Add planckian helpers for HSBType

[ccutrer]

No description provided.

[jimtng]

I wonder if we should call it white_cct, because we're looking at the spectrum from warm white to cool white, as opposed to "color" (i.e. the rgb mode).

The reason being, the word "white" is more user friendly, less esoteric than "planck", and I think it conveys the meaning directly.

Also white? and color? (the inverse of white?)

[ccutrer]

I wonder if we should call it white_cct

I've added aliases white_cct and white_cct?

Also would be very handy to add HSBType::WARM_WHITE and HSBType::COOL_WHITE although, some define cool white as 5000K (but some call this daylight) and some 6500K.

Yeah... the variety of what one thinks is warm to cool is why I don't plan on doing this.