Modifications to handle mapping the model-free space with the parameters S2f and S2s.
The remap script has been fixed (it was severely out of date).
The 'set_update()' function has been added to update S2 when either S2f or S2s are changed (and
neither S2f or S2s are None). A dummy 'set_update()' function now exists in the base class to avoid
problems.