Documentation for the Controllers folder + minor detail for previous docstrings

[jgrguric96]

This PR primarily contains the addition of docstrings for the files within the Controllers folder.
It also contains some small additions for the Agents folder files (such as type hints)

Luckily, a lot of context needed for the documentation was already done by mosaik itself with the requirements they have when inheriting the mosaik_api.Simulator class.

The missing docstring details can be expanded upon at a later date.

[manuGil]

Thanks for writing the doc strings. Please read my comment on specific files.
After that you can merge the changes. As a follow up, we should ask researchers to review and complete the missing information.