Update Polish translation
Italian translation: update

Sync'ed with 2e9f54b898ad757f98a40b627ab41eb7e2f7c3bb
Create a proper database upgrade method rather than dropping all tables.
Merge remote-tracking branch 'upstream/master'
Add comments regarding updating the database.
Fix order of columns
Merge branch 'Corly-master'
Merge branch 'zetok-translation'
Merge branch 'Ansa89-patch-2'
Changing version number
Fix wrong column
Merge remote-tracking branch 'upstream/master'