Rover: fixed CH_2 and CH_4 RC pass through

fixes issue #158
HAL_PX4: fixed startup bug in fmu_only mode
Copter: bug fix to accept HIL accel values correctly
Add set command to setup menu (and changed show command), same as for ArduCopter. Not included when building for 1280.
Copter: scale HIL accels consistently with Plane code