Local Documentation Builds

Local Documentation Builds

This adds configuration for performing local documentation builds
with the following simple command:

tox -e docs

This patch is part of our documentation effor to Move away from submodules
https://docs.opnfv.org/en/latest/how-to-use-docs/local-build-transition.html

added index.rst so that docs build succsesfully

Change-Id: I2d28f03ad4d5c9c14de095dc544257af9d1e51d9
Signed-off-by: Aric Gardner <agardner@linuxfoundation.org>
(cherry picked from commit 9666d8bb3df726d88d08d5811d2a99e713908396)