Ensure that the docstrings for the project are descriptive and up to date

[travishathaway]

What is the idea?

As we continue to open up conda with various plugin hooks, we would like to make sure that the code is easily read.

Tasks

Beta Give feedback

1. Add flake8-docstrings to pre-commit #12620
   cla-signed locked +2
   
2. Review all public module docstrings (see D100) #12668
   in-progress source::anaconda type::feature +3
   
3. Review all public class docstrings (see D101)
4. Review all public method docstrings (see D102)
5. Review all public function docstrings (see D103)
6. Review all public package docstrings (see D104)
7. Review all magic method docstrings (see D105)
8. Review all public nested class docstrings (see D106)
9. Review all __init__ docstrings (see D107)
10. Review nested README.mds (e.g. conda/core/README.md) and consider removing/combining into __init__.py docstrings

[jezdez]

The list of error codes are here: http://www.pydocstyle.org/en/6.3.0/error_codes.html