Remove unused colorFunctions file.
Implement formatting.

Converting of the AST back to string.
Don't treat CSS2 system colors as colors.

Identifying stuff like "window" and "background" as a color is clumsy,
nobody really uses these colors, one when one wants to he's better of
detecting them as special keywords by himself.
Support formatting objects.

Instead of requirering wrapping a single value object inside an array.