* preferences dialog - implement support for some xine prefs
* playlist queueing
* right-click menu for video window
* fix xine status message event processing in GtkXine and do something about
  them in the frontend - partially DONE
* reorganise and restructure.  XfmediaMainwin and XfmediaPlaylist should be
  gobjects, and XfmediaPlaylist shouldn't know anything about xine or GtkXine
  or about playing media. - XfmediaPlaylist is DONE.
* real detection of playlist files (by content, not extension) - DONE
* plugin ideas:
  - audioscrobbler
  - alarm
  - lirc/joystick control
