[release] version bump to 13.1 final
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 branch 'Gotham' of https://github.com/xbmc/xbmc into Gotham
Merge pull request #129 from quasar1/Gotham

Sync Gotham from test repo