(WIP) First chunk of code for new color selector

This commit is primarily archival; the new color selector is well
underway, but I'm having trouble wrapping my head around all the color
management bits, so I'm going to step away for a bit and see if I can't
sort things out.  At least I've got the basic elements rendering
properly using new HSV code.

RGB/HSV text boxes, etc are planned, so don't worry that it looks
unfinished at present...