Aggregate all sorts of tools configurations in pyproject.toml

[fwitte]

Having many configuration files (many of the files starting with . in the root) as well as the setup.cfg, setup.py and pyproject.toml at the same time really increases maintenance effort, since you always have to search multiple files to find what you are trying to change. Therefore, I suggest

• we move everything possible into pyproject.toml,
• delete setup.py and setup.cfg and
• put all configurations not available for pyproject.toml which were formerly in setup.cfg into their respective configuration files e.g. .flake8 as it seems

On top of that, I would like to critically review, what of all those things is actually required and take out the trash. E.g. the pep257 thing in setup.cfg seems ancient.

[fwitte]

For example, there are three configurations for the same thing:

.prospector.yml, [pydocstyle] and [pep257] (both in setup.cfg. According to http://www.pydocstyle.org/en/stable/usage.html#configuration-files this can be handled by pyproject.toml.