Bug fixes in the current parmest.py and example files

[slilonfe5]

Fixes # .

Summary/Motivation:

There is a raise error bug in the checks for experiment_outputs and unknown_parameters in the current parmest.py file: it fails to raise an error when the pyomo model used in the parmest example files lacks these attributes.

Changes proposed in this PR:

• Add a raise in the try and except code that checks for experiment_outputs and unknown_parameters in the current parmest.py file
• Add an experiment_outputs attribute to the pyomo model of the parmest examples that lack this attribute

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[slilonfe5]

@adowling2 @djlaky @mrmundt @jsiirola I fixed the parmest raise error bug that we talked about at the Tuesday Dev meeting. This should be ready for review.