Basic cells support

Adds support for running a region and child cell within a single
devstack environment.

README.md has been updated with some info on getting started.

Rebased/updated from initial work by Andrew Laski <andrew.laski@rackspace.com>.

Change-Id: Ic181da2180ccaa51df7efc9d66f7ccb820aac19b
diff --git a/README.md b/README.md
index 6570a14..1987db8 100644
--- a/README.md
+++ b/README.md
@@ -153,3 +153,23 @@
     MYSQL_HOST=$SERVICE_HOST
     RABBIT_HOST=$SERVICE_HOST
     Q_HOST=$SERVICE_HOST
+
+# Cells
+
+Cells is a new scaling option with a full spec at http://wiki.openstack.org/blueprint-nova-compute-cells.
+
+To setup a cells environment add the following to your `localrc`:
+
+    enable_service n-cell
+    enable_service n-api-meta
+    MULTI_HOST=True
+
+    # The following have not been tested with cells, they may or may not work.
+    disable_service n-obj
+    disable_service cinder
+    disable_service c-sch
+    disable_service c-api
+    disable_service c-vol
+    disable_service n-xvnc
+
+Be aware that there are some features currently missing in cells, one notable one being security groups.