Enable RC calibration mode during RC calibration to tell vehicle to ignore stick inputs for that period

Altitude splitted to altitudeAMSL and altitudeRelative, speed splitted to airSpeed and groundSpeed. PrimaryFlightDisplay uses airSpeed for FW and groundSpeed for MC.

Replace 9 seperate valueChanged() signals with just 1, and remove the resultant tons of code duplication

Vastly improved the joystick documentation, removed some redundant/unnecessary code, and fixed a couple of small bugs. This code should be ready for live testing.

The default UAS.cc now lists available actions that it can be commanded. These are polled by the Joystick Configuration window for each joystick button so that they can be assigned to trigger this action. Button presses don't yet trigger these actions, nor are they stored and reloaded on UAS switch.

The UASInterface now defines a systemCanReverse() function for indicating if the UAS is capable of commanding a reverse thrust.

Partway through refactoring of UAS deletion. This is in order to actually support removing UASes from QGC, which is currently impossible.

Partway through refactoring of UAS deletion. This is in order to actually support removing UASes from QGC, which is currently impossible.

Impl. Lorenz suggestions wrt one velocityChanged, altitudeChanged, speedChanged signal per reference frame. Impl. CDI on compass disk.

Changes for new calibration in APM 3.0 (Re: https://github.com/diydrones/MissionPlanner/issues/38), and change in some of the serial timeouts

Fix for crash when removing item from QuickView, and addition of more generic signal/slot combonation for property updates

Removed a lot of verbose debug output, added connection indication to main menu bar to improve situational awareness of operator

Added a unit test, setAirframeTest. Changed setAirframe function. Added an end_of_enum to the airframe enum.

Added remote OpenGL drawing in 3D view. Any external application can draw to the 3D view via the protobuf implementation of GLOverlay messages.

Removed some dead code.
Added more valueChanged() signals to account for every data type. This moves the conversion over into the valueChanged receivers, which while it will require more slot-functions, makes it easier to add more code as any necessary conversion is done internally to the slot and so the signaler doesn't need to know the details.
I also added some more details on the types of units expected by valueChanged().

Exposed HEARTBEAT.system_status and HEARTBEAT.base_mode to the realtime plotter widget via the valueChanged signal.