Re-enabled OSG support for Mac OS, for the 32bit build (64bit does not support Google Earth) the local 3D map is now enabled per default

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.

Added command to select target position for robot - command can be accessed via a right-click in the 3D View perspective --Lionel