Patch from Tony so the FDM can trim out a specific starting location for a

Patch from Tony so the FDM can trim out a specific starting location for a
joystick input, and then will ignore the actual position of that input
until the user places it in the proper position to match the trimmed position.
At that point the joystick input captures control over the value and the
value will match the joystick position from then on.  This is primarily set
up so that the FDM can trim in an initial throttle position.