New squidspeaker feature. Added fixed layout for navbar.

1) New squidspeaker feature: can now "clean up" the playlist to remove
   everything which the playlist, in its current configuration, won't
   play again (for instance, everything that's already been played if
   "loop" is off).
2) The navbar is now fixed to the top of the window.  On the
   squidspeaker playlist page, the main controls are fixed to the
   bottom of the window.
3) The squidspeaker playlist page autoscrolls to the current song when
   the song changes.
4) The space bar toggles play/pause now when in the squidspeaker
   playlist page.