Add basic nodepool documentation page

This initial basic nodepool document provides links to the manifests and
configuration for nodepool so people have a starting point to figure out
how it works, as well as a simple description of its purpose.

Change-Id: I3cc4e59e1e5ba4d62fd16c0da79d75352e9d78f0

doc/source/nodepool.rst

@@ -0,0 +1,34 @@
+:title: Nodepool
+
+.. _nodepool:
+
+Nodepool
+########
+
+Nodepool is a service used by the OpenStack CI team to deploy and manage a pool
+of devstack images on a cloud server for use in OpenStack project testing.
+
+At a Glance
+===========
+
+:Hosts:
+  * nodepool.openstack.org
+:Puppet:
+  * :file:`modules/nodepool/`
+  * :file:`modules/openstack_project/manifests/dev_slave_template.pp`
+:Configuration:
+  * :file:`modules/openstack_project/templates/nodepool/nodepool.yaml.erb`
+  * :file:`modules/openstack_project/files/nodepool/scripts/`
+:Projects:
+  * https://git.openstack.org/openstack-infra/nodepool
+:Bugs:
+  * http://bugs.launchpad.net/openstack-ci
+
+Overview
+========
+
+Once per day, for every image type (and provider) configured by nodepool, a new
+image with cached data for use by devstack.  Nodepool spins up new instances
+and tears down old as tests are queued up and completed, always maintaining a
+consistant number of available instances for tests up to the set limits of the
+CI infrastructure.

doc/source/systems.rst

@@ -13,6 +13,7 @@ Major Systems
    jjb
    logstash
    devstack-gate
+   nodepool
    jeepyb
    irc
    etherpad