Fix Issue #108: Update the API documentation of the ordinary regression
- Update the in-code documentation of the ordinary regression so it can be rendered nicely by Sphinx.
- Update the API section of the docs with the ordinary polynomial regression.
- Update the API section of the docs with the regression ABC.
- Conform to the black formatter.
- Update conf.py so methods of a class can be rendered without complaining about missing stubs (autodoc issue).
- Update conf.py so now the API elements (especially attributes of classes) are shown according their definition in the code, and not alphabetically.
This MR should resolve Issue #108 (closed) and partially Issue #86.