Converted the model-free return_conversion_factor() method to the new design.
The proton type is now set in all the model-free OpenDX system tests.
Fixed the call to generic_fns.value.set().
Fixed the references to self.file_prefix.
Passed the spin_id arg into the map_bounds() method.
Converted the model-free map_bounds() method to the new relax design.
Another small fix for the get_param_names() method.
Fixes for the get_param_names() base class method.
Fixes for the map_text() method.
Added a missing import.