modified the astrometry script so that is just updates the x/y locations in the MPC line.  This is to correct a bug in validate and is just a temporary usage change.  (also removed zscale code from displayable.py since that is no longer being used.  Finally:  workload no-longer exists when a user selects that they want to 'continue' if 'tracks' are complete.  This allows reviewing of a completed track file. The review process is not yet working.