Add tacker-horizon docs framework

[Nguyen Hai]

Currently, tacker-horizon does not have any documentation for user, admin, or contributor. It only has some guide files in the repo. In this report, I add a wishlist for tacker-horizon documentation.

Example Head-Dashboard: https://docs.openstack.org/heat-dashboard/latest/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/554874

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/554874
Committed: https://git.openstack.org/cgit/openstack/tacker-horizon/commit/?id=9c3bc53728ac7aec0c44e852c8c31e2b8da2f3ca
Submitter: Zuul
Branch: master

commit 9c3bc53728ac7aec0c44e852c8c31e2b8da2f3ca
Author: Nguyen Hai <email address hidden>
Date: Wed Mar 21 19:50:41 2018 +0900

    Add tacker-horizon docs

    This patch initially adds docs for tacker-horizon.
    Test: tox -e docs

    This patch also follow the new PTI for document build
    https://governance.openstack.org/tc/reference/project-testing-interface.html
    http://lists.openstack.org/pipermail/openstack-dev/2017-December/125710.html
    http://lists.openstack.org/pipermail/openstack-dev/2018-March/128594.html

    Change-Id: I18db38d7f4a2f979555470b2348f0bdaf1593fb5
    Closes-Bug: #1757096

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/tacker-horizon 0.12.0 release.