Begin work on teaching flight assist (aka setspeed) about frame of reference changes.
Incorporate partial changes towards this goal from flight stick branch.
First take on setspeed changes to deal with frame of reference changes.
Don't use speed locking for the progressive setSpeed modes - only use it for direct speed control (which upstream doesn't have yet).
Merge branch 'fix-flight-assistance' into improved-flight-control

Conflicts:
	src/LangStrings.inc.h
	src/ShipController.cpp
	src/ShipController.h
Integrate joystick flight controls with speed locking (set speed improvements)