Resolves some, but not all, `mypy` errors and moves to using Sphinx docs

[schuylermartin45]

This is a partial transition to enforcing mypy on the entire project.

I got ~2800 errors down to 833 errors. Some will be resolved upon the next percy version release.

This also updates the project to use the Sphnix docstring format.

The remaining 833 errors will be addressed at another time. Likely percy will need to be completely under the static analyzer before we can fully enable it in anaconda-linter