Add new manual "Cloud Administrator Guide"

With ChangeId I21cf53e26c25d75ad1b75ec7449e8e1a7e4b9bb2 the
Cloud Administrator Guide has been added to openstack-manuals.
These are the changes to publish it on docs.openstack.org

Change-Id: Ic1d0ad845e98f8b363e99a69354942d73f349d79
Merge "Add new manual "Cloud Administrator Guide""