Added FlxColorUtils

- New class `FlxColorUtils` containing over 30 new colors and the color
constants previously located in `FlxG` as well as color-related functions
previously located in `FlxU` added
- For the sake of backwards compatiblity, `FlxU` and `FlxG` still contain
the functions / variables, but they are just references to `FlxColorUtils`
and are documented accordingly
- The new colors have short descriptions from their wikipedia pages
- I had to create documentation for both conmpiler conditionals for each function and variable, because FD seems to behave really oddly in conjunction with these conditionals. Some vars are shown as `Int`, some as `BitmapInt32` for no appearant reason. IIRC though, `BitmapInt32` will be removed in Neko 2.0 so `FlxColorUtils` will be a lot less cluttered

Colors used in the console have not been changed, as the latest version of the console is on the `texture_atlas` branch.

#363