Addition of APM guided mode via right-click context menu in map view.
The right click menu will only show up when connected to an APM autopilot,
since this feature is APM only.
Major change to configuration, to allow for loading from APM generated xml

This commit still allows configuration widgets to be loaded from qgc files
assuming that there is no APM generated xml file (arduplane.pdef.xml) in
the files/%autopilorname%/ directory. This filename needs to be
configurable, and selectable at runtime. It is not yet.
Fix for incorrectly positioned tooltips on QGCToolWidgetItems