Plus a large number of other changes to allow for orderly shutdown of
objects without crashes or asserts. This is need for unit tests to
create/delete global state around every test.

- allow unit tests to use QGCApplication
- clear global singletons for each unit test run

Using QFileDialog directly on OS X can hang intermittently due to Qt
bug.

Checkpoint: RC calibration much better / operation, can use UI tweaks. Airframe config in, but not operational and still very functional / ugly.

Removing UASes now returns the UI to an almost pristine state. This was done by altering the activeUASSet signal so that it can emit a NULL UAS. Crashes may still exist in autopilot-specific code.

Removing UASes now returns the UI to an almost pristine state. This was done by altering the activeUASSet signal so that it can emit a NULL UAS. Crashes may still exist in autopilot-specific code.

Added not yet working version of logging / log replay, fixed ALL bugs in main window, enabled full persistence in main window and serial link.

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

Working on QGraphicsView-based local waypoints interface supporting drag-and-drop, commented code, fixed Google Maps interface, added mouse and SpinBox zoom to HSIWidget, fixed MAV-based coloring and stylesheets - MEGA COMMIT

Cleaned up and commented major code parts. Refactoring HDD and HSI widgets to support QGraphicsView drag-and-drop, tested multi-MAV support more intensely, currently adding the system coloring to all widgets