[release] version bump to 13.1 final
[lang] update of internal addon language files
[lang] update of core language files
[lang] update of skin.confluence language files
Merge pull request #4793 from MartijnKaijser/13.1

13.1
[lang] update of internal addon language files
[lang] update of core language files
[lang] update of skin.confluence language files
Merge remote-tracking branch 'upstream/Gotham' into Gotham_dsplayer