view: Add method to play a playlist in Playlists view

https://bugzilla.gnome.org/show_bug.cgi?id=729309
player: Add new signal 'playlist-changed'

https://bugzilla.gnome.org/show_bug.cgi?id=740211
mpris: Implement TrackList interface of MPRIS

https://bugzilla.gnome.org/show_bug.cgi?id=740211
mpris: Implement Playlists interface of MPRIS

https://bugzilla.gnome.org/show_bug.cgi?id=729309
mpris: Add Fullscreen and CanSetFullscreen properties

Introduced in MPRIS 2.2.

https://bugzilla.gnome.org/show_bug.cgi?id=740212