parmest: allow user to specify path to ipopt executable

[adowling2]

This would be a nice enhancement for folks with multiple versions of Ipopt installed. Alternately, we could let the user provide an Ipopt solver object.

[DLWoodruff]

I'll try to add this feature.

[adowling2]

@djlaky Is this issue now obsolete with the parmest refactor?

[djlaky]

@djlaky Is this issue now obsolete with the parmest refactor?

@adowling2 If solver_options is sufficient, I think it has been addressed:

pyomo/pyomo/contrib/parmest/parmest.py

Lines 258 to 260 in 06452a9

	solver_options: dict, optional
	Provides options to the solver (also the name of an attribute).
	Default is None.