This patch adds Zaqar-specific contents of the OpenStack Installation
Guide in the Zaqar repository per [1]. It only covers installation on
Red Hat-based systems.
Also this patch adds tox.ini environment for install-guide and adds
openstackdocs-theme to test-requirements.txt.
The Zaqar Installation Guide structure is based on Install Guide
Cookiecutter: https://review.openstack.org/#/c/314229/.
[1] http://specs.openstack.org/openstack/docs-specs/specs/newton/project-specific-installguides.html
Change-Id: I72300c146b22511da4432775fc84e8c821a3fd12
Implements: blueprint install-guide-in-tree
Partially-Implements: blueprint projectspecificinstallguides
5134d3018b