playlist: Improve speed in PlaylistQuery class
playlist: Improve speed in PlaylistQuery class

Implement the col_clause method for faster, sqlite-based querying. This
will only make a difference if the "fast" kwarg is set to True.

shamangeorge/beets,shamangeorge/beets,beetbox/beets,jackwilsdon/beets,beetbox/beets,ibmibmibm/beets,beetbox/beets,SusannaMaria/beets,beetbox/beets,sampsyo/beets,sampsyo/beets,jackwilsdon/beets,jackwilsdon/beets,ibmibmibm/beets,SusannaMaria/beets,ibmibmibm/beets,SusannaMaria/beets,shamangeorge/beets,jackwilsdon/beets,sampsyo/beets,sampsyo/beets,SusannaMaria/beets,ibmibmibm/beets,shamangeorge/beets