playlists: Add new method for getting path to a playlist
playlists: Add method for parsing playlists
view: Add songs list view to Playlists view
grilo: Check for grilo filesystem plugin
grilo: Add method to get a media object from uri
playlists: Use grilo to return media objects when parsing
grilo: Connect signals to registry first before loading plugins
playlists: Skip unexistent files
grilo: get fixup
playlist fixup
view: Load songs of playlist when selected
view: Monitor playlist songs
view: Update model when current track changes
grilo: Use synchronous get_media_from_uri

The async one causes segmentation faults.
view: fixup for missing iter
view: Play song when activated