Convert README.rst to README.md

Since PyPI accepts Markdown formatted README.md, there is less reason to use the more complicated syntax of ReStructured Text .rst files. We have converted hundreds of README.rst to README.md with the process below.

Bulk convert RST .rst to Markdown .md:

pandoc -f rst -t markdown README.rst -o README.md

Slight hand correction: remove most \ that were inserted (find and replace with nothing)

Replace in Git repo:

git rm README.rst
git add README.md

For Python repos, be sure that pyproject.toml is configured for README.md