Update Polish translation
Solve additional opening of the MainActivity from WelcomeActivity and deal with the back button pressed situation.
Merge remote-tracking branch 'upstream/master' into work
Add Ukrainian language
Merge branch 'ukrainian-language'
Merge branch 'Corly-work'
Merge branch 'zetok-translation'
Merge branch 'Ansa89-master'
Merge branch 'master' of https://github.com/sk8ter/Antox into sk8ter-master
Merge branch 'sk8ter-master'
Merge pull request #10 from Astonex/master

Sync with main project