display constraints report graphically in jupyter notebook

[dave-doty]

There is a function create_report (new link once name changes: create_text_report) that returns a string showing the results of evaluating constraints. It is what is written to the report_*.txt files during the search.

For visualizing, implement a function that can display the data graphically using matplotlib in a Jupyter notebook. Since the user will want to visualize the "raw" data such as NUPACK complex free energy, rather than the score values into which these are converted, this will involve refactoring the return value of SingularConstraint.evaluate and BulkConstraint.evaluate_bulk.