Add Python wrappers for Equation and Interpreter classes

Issue/feature addressed

Adds Python bindings for the Interpreter and Equation classes.

Proposed solution

Python bindings now incorporate support for the Interpreter and Equation classes.

Implementation

See above.

Tests

Notes

In addition to the bindings, a new metric has been added to the tester to provide better support for the Python unittest module. New tests have been added, and the existing unit tests have been modified to use the new metric.

Checklist

• Functions and classes, or changes to them, are documented.
• User guide/documentation is updated.
• Changelog is updated.
• Suitable tests added for new functionality.
• Newly added files are correctly formatted.
• License added to any new files.
• No extraneous files have been added (e.g. compiler output or test data files).