Bugfix for github issue #672.
File modifcation date used to test for changes got out of sync after introduction of intermediatefilelookup.plist files.
Changed publishing status update message for spritesheets, now without plist extension for current filename.
Modification dates of directories needed to be ignored to work properly with intermediate filelookups.
Merge pull request #674 from NickyWeber/bugfix/#672_always_full_publish

Bugfix for github issue #672.