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/stack.sh b/stack.sh
index c0a314d..37abd6d 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1034,6 +1034,8 @@
         LIBVIRT_FIREWALL_DRIVER=${LIBVIRT_FIREWALL_DRIVER:-"nova.virt.libvirt.firewall.IptablesFirewallDriver"}
         iniset $NOVA_CONF DEFAULT firewall_driver "$LIBVIRT_FIREWALL_DRIVER"
     fi
+
+    init_nova_cells
 fi
 
 # Extra things to prepare nova for baremetal, before nova starts
@@ -1094,14 +1096,19 @@
     create_quantum_initial_network
     setup_quantum_debug
 elif is_service_enabled $DATABASE_BACKENDS && is_service_enabled n-net; then
+    NM_CONF=${NOVA_CONF}
+    if is_service_enabled n-cell; then
+        NM_CONF=${NOVA_CELLS_CONF}
+    fi
+
     # Create a small network
-    $NOVA_BIN_DIR/nova-manage network create "$PRIVATE_NETWORK_NAME" $FIXED_RANGE 1 $FIXED_NETWORK_SIZE $NETWORK_CREATE_ARGS
+    $NOVA_BIN_DIR/nova-manage --config-file $NM_CONF network create "$PRIVATE_NETWORK_NAME" $FIXED_RANGE 1 $FIXED_NETWORK_SIZE $NETWORK_CREATE_ARGS
 
     # Create some floating ips
-    $NOVA_BIN_DIR/nova-manage floating create $FLOATING_RANGE --pool=$PUBLIC_NETWORK_NAME
+    $NOVA_BIN_DIR/nova-manage --config-file $NM_CONF floating create $FLOATING_RANGE --pool=$PUBLIC_NETWORK_NAME
 
     # Create a second pool
-    $NOVA_BIN_DIR/nova-manage floating create --ip_range=$TEST_FLOATING_RANGE --pool=$TEST_FLOATING_POOL
+    $NOVA_BIN_DIR/nova-manage --config-file $NM_CONF floating create --ip_range=$TEST_FLOATING_RANGE --pool=$TEST_FLOATING_POOL
 fi
 
 if is_service_enabled quantum; then