Save in TagPro format too

Adds support for saving a PNG compatible with TagPro. The new file has
the same name as the original, except that it ends in the suffix
".tagpro.png" instead of just ".png".
Make sure the TagPro image uses the same UUID

The code was generating new UUIDs for both the main image and the
TagPro image; this makes it use the same for both.
Merge branch 'master' into tagpro-format

Conflicts:
	level_gen.py
Fix X/Y swap

This code worked properly before the merge, but now it has the X and Y
co-ordinates the wrong way round. Fixing.
Swap width/height

Apparently I forgot to swap these, too. Whoops.
Merge pull request #1 from Sophira/tagpro-format

Add TagPro format saving