adding in initial version of texture unpacker.

I started this work over on Esoteric software forum here:
http://esotericsoftware.com/forum/viewtopic.php?f=11&t=2030&p=12001&hilit=unpacker#p12001

I still need to add a few other things such as unpacking nine patch files and add in some tests but I figured it wouldn't hurt to get this initial pull request in.