FlightGear - Flight Simulator FGAddon

Harrier-GR3: autohover AoA: also allow control via alt-x and alt-w.

These keys are easier to reach when landing than alt-insert/delete.

Harrier-GR3: autohover AoA: disable if weight on wheels.

Avoids unwanted accelerating after landing.

Harrier-GR3: auto-hover: use properties to store target height / vertical speed.

Also, don't override auto-hover properties that were pre-set by command line
--prop:<name>=<value>.

These changes for example allow target position/height to be set from command
line, becoming active after take off.

Harrier-GR3: auto-hover: hacky attempt to improve high-speed behaviour.

Harrier-GR3: autohover: hide windows properly when inactive.

Harrier-GR3: auto-hover: alt-/ targets current position.

Also made Alt-, cancel click targetting if pressed twice, and show text to
indicate next click will set target position.

Harrier-GR3: minor improvements to HUD.

Show more of the attitude ladder. Moved altitude numbers down slightly so they
don't overlap with heading numbers.

Harrier-GR3: improved autohover AoA nozzle pid controller - just look at vertical component of AoA.

Helps to avoids unhelpful increases in speed via nozzles when we are turning.

Harrier-GR3: improved autohover AoA behaviour - slow down corrections.

Harrier-GR3: autohover: leave horizontal target mode active even after touching ground.

No need to cancel target mode after touchdown.