Switch to NumPy Style Python Docstrings

[LockeErasmus]

I have decided we will eventually use Sphinx, so from now on, please use NumPy style for creating new docstrings. When possible, change existing docstrings to this style also.

NumPy docstrings styleguide: https://numpydoc.readthedocs.io/en/latest/format.html
NumPy docstrings examples: https://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_numpy.html
Sphinx: https://www.sphinx-doc.org/en/master/

By the way, it supports LaTex via mathjax I think, check for instance airy function from:

https://github.com/scipy/scipy/blob/9492369e7f76c8206ac1c375e75375ca7410a7e7/scipy/special/add_newdocs.py#L312