       Stop all sub motion.

     Full stop will stop all forward/backward, up/down and left/right motion
   with one key-stroke. Very useful if things get a little out of hand,
   as might happen while trying to follow fast moving denizens of the deep.

     If a mouse is present (on the desktop, not in the sub) left clicking
   on the throttle or attitude indicator will reset only the corresponding
   motions.
