math: implement bound_sym() in terms of bound_min_max()
Merge pull request #478 from solidgoldbomb/simpler-bound-sym

math: implement bound_sym() in terms of bound_min_max()
Change SystemSettings UAVO to represent that the data is no longer GUI
configuration data, but is instead encoding the airframe setup.
Add new trim UAVOs
Added new TrimAngles UAVO to all targets.
Added autopilot level trim to Stabilization module.
Added UI support for setting actuator trim and level bias values on fixed-
wing platforms.
Changes requested in review.
Added new control mode, Enhanced Attitude. Enhanced Attitude uses the trim
angle as the attitude setpoint.
Fixes bug by which attitude trim leveling could not be used when in
EnhancedAttitude stabilization mode.