Clarify public/private: create prelude

[nicholas-miklaucic]

I need to clarify what's public and what's private: I think pretty much everything should be public, but that might create problems down the line. What, if anything, should be private?

We also need a "prelude" of sorts. This allows people to import things without having to dig through a bunch of files. I'm thinking Color, RGBColor, CIELABColor, CIELCHColor, XYZColor, Mix, and ColorPoint.

[nicholas-miklaucic]

Done.