Use notify-send as fallback instead of gtkdialog

  We'll be getting all of the requirements for this in -current
    real soon now, so unless I snuffed something up, this should
    be really close to what we need.  :-)
Renamed from blueman_open to blueman-open
More major upheaval in the code...

  * no more gvfs usage - that was a disaster
  * better handling of the notifications