Code Cleanup, Nextcloud Infrastructure

[rotdrop]

• [x] move JS code to Vue where feasable
  • [x] personal settings
  • [x] admin settings
• [x] app-store registration, see #2
  • [x] either rename the app or make the author of the existing RC apps transfer his ownership
    • [x] rename the app to mail_roundcube
    • [ ] ~transfer ownership of roundcube app in app-store~
  • [x] request code signing certificate
  • [x] obtain certificate for code signing
  • [x] register the app
  • [x] upload a pre-release to the appstore to verify things work
  • [x] release the first version v1.0.0
• [x] use Transifex for translation
• [x] coding style clean up where not already done

[rotdrop]

Ok, so in principle the first "real" release could be emitted. Of course, it will be buggy ...