Fix#257, you should be able to clear username and title patterns
now with ease. For best results, wait until they've wasted a lot
of time adding a lot of videos before you wipe them.
Any user with playlistdelete permission can now use the /clean
command to wipe out a user's additions to the playlist. This
can be helpful for taking down abusive items en masse without
resetting the entire playlist.
The code should probably be generalized, somehow, to handle
title patterns or additions within a certain timeframe.
