[Feature] include Actors Metadata on "movieinformation"-window

- script.metadata.actors is now integrated in DialogVideoInfo (press "i"
in Video Library)
- destroy all overlay dialogs when going back to home menu (especially
movieinformation and actors metadata)
[Feature] changed Now Playing toast widget

- remove remaining time (especially because Audio Podcasts and Radio
Shows longer than 59 minutes weren't reported correctly)
--> more room for Track/Artist info
- [fix] Artist Fanart on MusicOSD
- remove Artist Slideshow(...) for now