Introduce FlxSort for FlxTypedGroup.sort() to improve performance
Make FlxSort.byValues() compatible with inlining
Merge branch 'dev' of https://github.com/HaxeFlixel/flixel into FlxSort

Conflicts:
	flixel/group/FlxSpriteGroup.hx
	flixel/group/FlxTypedGroup.hx
Remove FlxSort.byX() - doesn't seem to useful
FlxSort: remove remaining reference to byX()
Merge pull request #858 from Gama11/FlxSort

Introduce FlxSort for FlxTypedGroup.sort() to improve performance, closes #837