search: return to search results when Back pressed
artists: fix pep8 error
widgets: remove remains of Gio-based file monitors
widgets: Rename variable playlist to playlists
widgets: Add PlaylistWidget
view: Use PlaylistWidget in Playlists view
window: Properly get the model for Playlists view
query: Add queries for searching with matching playlist name

This also updates queries for any field matches to check if the search
text is a playlist name.
searchbar: Add Playlist to Match options
view: Add Playlist to Match options
query: Add queries for searching Playlists
view: Show playlists in search results
view: Fix selection on playlists in search results
window: Remove playlist too in Search view
view: Close Search view when showing playlist and it was deleted
query: Allow changing the solution sequence modifiers
query: Sort songs by title in search results
widgets: Rename add_playlist_iter to addPlaylistIter
widgets: Select playlist if already exists in Add to Playlist dialog

https://bugzilla.gnome.org/show_bug.cgi?id=728331
widgets: Use list box in Add to Playlist Dialog