Use libnotify instead of Qt's notifications.

Qt implements it's own notifications (which have a Windows XP-like appearance) instead of using the system ones (eg: libnotify's)
Aside from theming, this has a few other inconveniences, such as location, visibility, timeout, and any other feature the user's notification daemon may provide.

This *does* add libnotify as a dependency, though I belive most desktop users will already have this installed.