Remove a lot of formula_expression_ref from smodel/setup.C
Eliminate formula_expression_ref( ) from smodel/setup.C
Remove formula_expression from imodel/setup.C
Eliminate formula_expression_ref from arguments to Parameters.
Correctly prefix the submodels.
Remove add_submodel( ), find_declared_parameter( ), etc.
Remove Model_Notes from Context, and remove formula_expression_ref.