Add cacti documentation

Initial commit for basic cacti documentation and how to add a
new host to our instance.

Change-Id: I16f3474c5e0355ea10d4bffc94925624ee64328a

doc/source/cacti.rst

@@ -0,0 +1,34 @@
+:title: Cacti
+
+.. _cacti:
+
+Cacti
+######
+
+The `Cacti <http://www.cacti.net/>`_ network graphing tool
+is installed on cacti.openstack.org.
+
+At a Glance
+===========
+
+:Hosts:
+  * http://cacti.openstack.org
+:Puppet:
+  * :file:`modules/openstack_project/manifests/cacti.pp`
+:Projects:
+  * http://www.cacti.net
+:Bugs:
+  * http://bugs.launchpad.net/openstack-ci
+  * http://www.cacti.net/bugs.php
+:Resources:
+  * `Cacti Documentation <http://www.cacti.net/documentation.php>`_
+
+Overview
+========
+
+Cacti is accessible via the web here:
+
+http://cacti.openstack.org/cacti/graph_view.php
+
+New servers are added to our cacti instance by adding the host to the
+:file:`modules/openstack_project/manifests/cacti.pp` file.

doc/source/systems.rst

@@ -6,6 +6,7 @@ Major Systems
 .. toctree::
    :maxdepth: 2
 
+   cacti
    gerrit
    jenkins
    zuul