Added 2D Sprite support

As talked about here-[Making a 2D Sprite based game](http://www.gameplay3d.org/forums/viewtopic.php?f=7&t=453&sid=526fe0a1a83780dcbdb7ec798f89c2bc), 2D Sprite support in GamePlay.

Note: I don't have a Mac so I couldn't modify XCode's project with the Sprite code.