view: Check if playlist is playing before checks on remove entry

When deleting an entry in the playlist, check first if the playlist is
indeed running before checking if the entry is currently playing.
view: Remove filtering in Playlists view
window: Don't directly get the model in child stacks
widgets: Add selection mode to ArtistAlbums

This is for selection mode in Search view when selecting an artist.
view: Implement selection mode in artist view in Search
widgets: Update selection menu when a row changes in ArtistAlbums
toolbar: Check selection mode before state on update
searchbar: Disable Match if not searching with Tracker

Since we can't control what fields could be matched in sources not
using SPARQL queries, disable Match in the dropdown unless we are
searching in Tracker.