Brand new FlxColor, closes #1027

A demo (also pushed to demos) can be found here: https://dl.dropboxusercontent.com/u/28458706/colors.swf

**Change summary**
* Removed FlxColorUtil
* FlxColor is now instantiable
* FlxColor is abstract int, interchangeable with Ints/hex literals
* FlxColor provides properties for getting and setting individual RGBA/float RGBA/HSB/HSL/CMYK values
* Reimplemented conversion algorithms to reduce code repetition
* Added gradient generation with optional easing
* Added orange to color presets
* Changed all Ints that are used as colors to FlxColors
* FlxMath.wrapValue can now wrap negative values
* Some code tidying + import organizing