Regularize ColorUtilities methods

The method names in ColorUtilities are a bit verbose, and not regular (in that there is a method to add transparency, but not one to take it away).

I propose to deprecate "setTransparencyInColor" and add "toTransparentColor" which does the same thing with a "better" name. Then propose adding "toSolidColor" as the obverse. This will regularize the functions in here better, while still leaving the old method (deprecated) for backward compatibility.

Next step would be changing all the callers to use the new method(s).