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.

Fixed Compiler Error C2864 - only static const integral data members can be initialized within a class

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.

Have settings loaded/stored correctly for all joysticks based on their UAS type and autopilot type. Switching between UASes doesn't work right yet, however.

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.

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