AP_Compass: added COMPASS_ORIENT parameter, to support external compasses

this allows the user to configure the compass for any orientation
supported by our rotation library
Rover: updates for new compass API
Copter: updates for new compass API
Plane: updates for new compass API
Tools: updates for new compass API
AP_AHRS: update for new compass API
AP_Declination: fixed example build
AP_Compass: removed old orientation defines

we now use the rotations in libraries/AP_Math/rotations.h