Summary:
This diff makes the ColorValue export "official" by exporting it from StyleSheet in order to encourage its use in product code.
Changelog: Moved ColorValue export from StyleSheetTypes to StyleSheet
Reviewed By: TheSavior
Differential Revision: D21076969
fbshipit-source-id: 972ef5a1b13bd9f6b7691a279a73168e7ce9d9ab