Ardupilot support, builds now cleanly on Windows. Fixed a bug where the application could crash if no system was connected.

Still need to add uas connections. New osgwidget inherits from
qgraphicsview to expose more functionality to qt. Map3d.ui contains
the graphics view and some buttons. Currently runs yahoo_heightfield
by default. Make sure you run qgroundcontrol fromt the top dir or
it will seg fault, :-). I'll add some error handling soon.

Fixed image cache bug: when a cache is full, a new image replaces the first cached image instead of the oldest cached image.

Latest working version of 3D imagery overlay. Unresolved errors with Google URLs for satellite imagery.