Implementation of SRF API v3

[tobiaswaldvogel]

Contents:

• Implementation of new SRF api v3
• Add fanart to all items (looks much better in standard Kodi skin)
• Support for subtitles
• Use urn instead of video id
• Use inputstream adaptive if available (if not Kodi falls back to ffmpeg)
  Advantage:
  Stream is chosen on network speed and automatically adapted
  Playback starts much faster

[goggle]

Thanks for this @tobiaswaldvogel
I will merge and prepare a new release.