convert everything to new mp.set_manager syntax #6

The transition to the use of mp.set_manager to handle the fields of opt_model resulted in many methods of opt_model being deprecated. The use of these deprecated method calls needs to be removed from all MP-Opt-Model examples and tests, as well as from the MATPOWER and MOST distributions.

The deprecated methods and their new counterparts are ...

• om.add_named_set() --> om.(sm).add()
• om.describe_idx() --> om.(sm).describe_idx()
• om.getN() --> om.(sm).get_N()
• om.init_indexed_name() --> om.(sm).init_indexed_name()
• om.add_lin_constraint() --> om.lin.add()
• om.add_nln_constraint() --> om.nle.add(), om.nli.add()
• om.add_nln_cost() --> om.nlc.add()
• om.add_var() --> om.var.add()
• om.eval_lin_constraint() --> om.lin.eval()
• om.eval_nln_constraint_hess() --> om.nle.eval_hess(), om.nli.eval_hess
• om.eval_nln_constraint() --> om.nle.eval(), om.nli.eval()
• om.eval_nln_cost() --> om.nlc.eval()
• om.eval_quad_cost() --> om.qdc.eval()
• om.init_indexed_name() --> om.(sm).init_indexed_name()
• om.params_lin_constraint() --> om.lin.params()
• om.params_nln_constraint() --> om.nle.params(), om.nli.params()
• om.params_nln_cost() --> om.nlc.params()
• om.params_quad_cost() --> om.qdc.params()
• om.params_var() --> om.var.params()
• om.set_params() --> om.(sm).set_params()
• om.varsets_cell2struct() --> mp.sm_variable.varsets_cell2struct()
• om.varsets_idx() --> om.var.varsets_idx()
• om.varsets_len() --> om.var.varsets_len()
• om.varsets_x() --> om.var.varsets_x()