* Convert README from Markdown to ReStructured Text and use as longdesc
Discussion in #13758 led to deciding to switch README to rst and having
setup.py consume it as the long_description.
* Fix long string in setup.py for pep8 compliance
* Open README.rst as read-only
* Update usages of root README.md to README.rst
Unsure about the file ./packaging/debian/docs as it (only) contains the
text README.md. I believe it's referencing ./packaging/debian/README.md
but maybe someone who knows debian packaging could review it?
* Pick up fixes that had been merged into README.md after the initial conversion to rst
These values are used by software updaters to show which applications
are being updates to the user. In the case of Ubuntu, it will now show
clearly that it is updating Ansible instead of a radically simple IT
automation platform.