Add filter rendering for BitmapData for users that use OpenGL

[Cheemsandfriends]

The title already says it all, Basically, every BitmapFilter, altho it has great use for DisplayObjects with a vast and very detailed procedure on how to apply a filter to a bitmap, this can't be said to BitmapDatas.

As far as I can understand, they are locked on what would be a procedure that's CPU based, for rendering types like Cairo or Canvas without the use of OpenGL, but no implementation on the OpenGL side.

I know this is pretty much possible due to me doing very hacky stuff to implement a BitmapData that can collect several pieces and then apply a filter to them, for my projects at HaxeFlixel, altho this may require some kind of reorganisation of how filters may be applied.