Some features that would be nice for a final Gobby 0.5 release. We could
perhaps do pre-releases with some of these missing before:

 - Implement self-hosting, this also requires showing and handling directories
   in InfGtkBrowserModel/Store
 - Sort BrowserModel in Left pane and DocumentLocationDialog
 - Add base preferences class with Preferences::Option definition to util/,
   inherit in core/, move ClosableFrame to util/
 - Show in tab and userlist when others are typing, using an icon
 - Typing sounds (libcanberra?)

These things need to be implemented in infinote, but again would be nice
to have:

 - Show other user's cursors
 - Show other user's selections
 - Show other user's viewport position (perhaps in a separate widget)
