This patch adds to "docs" tox job ability to automatically
generate sample config file and config reference based on
config options defined in code.
Change-Id: Id960cc28d1b13ef3ed15e911f59620afb83f45b9
This also improve other documentation pages and add many
cross section references.
This guide has been tested on CentOS 7 (Python 2.7) and
RHEL8 (Python 3.6).
Change-Id: I827dcf7237792ab94286c960968df405c7e548b9