Formatting of code: indentation.
SpriteSheetPacker Tupac returns now a list of files created.
Published png files stored in set. Removed some debug NSLogs. Renamed some local var to be more self-explanatory.
Renamed project settings property, it didn't make sense.
OptiPNG run as last step in publishing process.
Still some tweaks needed: Skip if file is up to date, update progress window, add warnings.