Update documentation

[jrsmith3]

Overview

This issue is a placeholder for the time being, but I know that I will need to update the docs once I make all the changes for release 2.0.0.

Related issues

• Depends on Refactor SQSolarcell and DeVosSolarcell classes #77.

I will merge the PR for #77 into the release 2.0.0 epic branch, merge the epic branch into the branch corresponding to #76, then continue hacking until I'm able to merge #76.

[jrsmith3]

I am using numpydoc for the docstrings in the codebase and I would like to use Python type hints instead of declaring the types in the docstring itself. Looks like someone has asked for this feature in numpy/numpydoc#196.

[jrsmith3]

Someone mentioned the napoleon extension for sphinx that leverages PEP 484 and PEP 526 docstrings. I'll consider using it instead of numpydoc.

[jrsmith3]

I need to make sure that as part of this PR I mention that the docstrings in this module use the numpy style.

[jrsmith3]

I am going to need to do some editing to the mathematical parts of the documentation, particularly with method docstrings. I want to avoid repeating myself (repeating lists of symbols, etc.) but I also want the explanations to be clear. For example, at the time of this comment I am giving the integral representation in BEI.upper but not the expression after the integral has been computed. I should consider giving both.