Spritemap functionality & FP's getXML functionality

Created a very basic version of FlashPunk's Spritemap functionality. At the moment all it can do is add & play animations. The biggest difference to FP's implementation is of course the usage of texture atlases over spritesheets.   It also assumes you're using the naming convention of "animationName_x" in your atlas XML.

I've also added FP's getXML() function to the SP helper class, useful for reading those texture atlas data files and if you're using a level editor other than OGMO.