Keeps private playlists in the list, for their owner.

Adds only this user's playlists, when one is created or comes back into view. Without it, anyone's are added.

The order the list is in, for one the API sorts: the playlists page's and a profile's. A list in an order of its own leaves it out, the followed playlists being by the date they were followed and a search's results the search's: it takes no new playlist, since the socket says neither what the user follows nor what a search matches, and moves none. Playlists already listed still change, go, and come back where they were.