Convert docstrings into standard (propose Google) docstring format

[sadielbartholomew]

Presently the docstrings in the codebase are in some format I do not recognise, so we should convert them into a standardised format that is recognised by the Sphinx docs builder.

Since cf-python uses a format closely aligned with the Google standard, it makes sense to be consistent with that and to use the same, so that is my choice unless anyone has any objections.