Instead us a Toolbox concept which hangs off of QGCApplication

This is in preparation for full Qml main window

- select active vehicle
- arm/disarm
- select flight mode

Signed-off-by: kai <kai@uav-flightresearch.com>

- MultiVehicleManager is a Qml friendly replacement for UASManager
- Vehicle is a replacement for both UAS and AutoPilotPlugin

- FirmwarePlugin is the new place for code which is specific to
firmware flight stack
- FirmwarePlugin currently supports flight mode apis
- Modify code to use new FirmwarePlugin support

- All resources are either under src or under resources dirs
- Removed files top level directory
- Move flightgear files to top level dir

Also many LinkManager API changes to further isolate all link
management inside LinkManager.

Waiting for real fix to put back. Issue #1275

Removed "Clear Text" context menu from roll down dialog
Fixed "Clear Text" context menu in Info Dialog (renamed to "Clear Messages" in the process)

Shrunk the Message drop down dialog a bit.
Made the Message drop down dialog slightly transparent.

The goal of this first installment is to organize the code a bit so it's more readable,
clean up a bit of left over cruft, and manage link configurations (and links in general).

No need to force them to show

No need to force them to show

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.

This function is called automatically when a QSettings object is destroyed,
so is rarely needed to be called explicitly.

There are still some cases where
a QSettings object is passed-by-reference, so there I left the sync() calls as
it's unclear how permanent those objects are and if they'd call sync() before
application shutdown

- 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.