Flixel nme

FlxSprite filters added, working fine, cpp target not tested yet.

For effects like outer glow, or drop shadow, user may need to increase the sprite size, using a graphic with a margin width and height with zero alpha, thats what i used to do.

Ill be working in a way to increase the sprite size (alpha zero margin) using only a method. 
And use that method when adding an effect like outer glow or dropShadow, either by adding a adjustMargins:Bool = true, to the addFilter() or/and making the method public so the user increases the margin by a specific width and height.