Tile-Set swapping

[GoogleCodeExporter]

Add ability to choose a type of map to play on, perhaps with minor
variations between the layouts that will add more replayability.

This will require branching the main tileset.png into one for tiles and one
for player animation, which is a long resisted change ;)

Original issue reported on code.google.com by mazemast...@gmail.com on 29 Apr 2009 at 4:29