Fix for #1153, #1162 and Added Functionality for Limited Play

Now uses SetMarkerReq instead of AddMarkerReq and RemMarkerReq, but I'm
going to rewrite SetMarkerReq to display prettier trace information, and
then add the CompoundCall to other marker modifying spots.  Right now,
the Python API's marker functions don't pass through the marker's set
method, and never get compounded.