Review linking of markdown files in docs directory

Copying/linking generated root-level markdown files (README.md, CHANGELOG.md, CONTRIBUTING.md, and MANIFEST.md) in the docs directory is not a good idea, for the following reasons:

• These files contain repository-related, not library-related information
• Since the original files are located at the root-level of the generated repository, file links that work in Gitlab/Github do not work when these files are processed by Sphinx
• The recommonmark 0.6.0 Sphinx extension used for parsing these markdown files raises a lot of runtime errors, so it is not realiable for production

Which information really needs to be stated in both the repository description files and the library/application's docs is debatable, but probably not a great deal.