Create service definition for nova-serialproxy

Nova has the ability to do remote interactive consoles but there is no
easy way to enable this in devstack.  This change defines a service
called n-serial to enable the service.  Documentation is added to a
new guide on nova, describing how to set further options in local.conf

Change-Id: I401d94b2413c62bfae9b90d2214d77bd4cfc15d5
diff --git a/doc/source/guides/nova.rst b/doc/source/guides/nova.rst
new file mode 100644
index 0000000..0d98f4a
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+++ b/doc/source/guides/nova.rst
@@ -0,0 +1,72 @@
+=================
+Nova and devstack
+=================
+
+This is a rough guide to various configuration parameters for nova
+running with devstack.
+
+
+nova-serialproxy
+================
+
+In Juno nova implemented a `spec
+<http://specs.openstack.org/openstack/nova-specs/specs/juno/implemented/serial-ports.html>`_
+to allow read/write access to the serial console of an instance via
+`nova-serialproxy
+<http://docs.openstack.org/developer/nova/man/nova-serialproxy.html>`_.
+
+The service can be enabled by adding ``n-sproxy`` to
+``ENABLED_SERVICES``.  Further options can be enabled via
+``local.conf``, e.g.
+
+::
+
+    [[post-config|$NOVA_CONF]]
+    [serial_console]
+    #
+    # Options defined in nova.cmd.serialproxy
+    #
+
+    # Host on which to listen for incoming requests (string value)
+    #serialproxy_host=0.0.0.0
+
+    # Port on which to listen for incoming requests (integer
+    # value)
+    #serialproxy_port=6083
+
+
+    #
+    # Options defined in nova.console.serial
+    #
+
+    # Enable serial console related features (boolean value)
+    #enabled=false
+    # Do not set this manually.  Instead enable the service as
+    # outlined above.
+
+    # Range of TCP ports to use for serial ports on compute hosts
+    # (string value)
+    #port_range=10000:20000
+
+    # Location of serial console proxy. (string value)
+    #base_url=ws://127.0.0.1:6083/
+
+    # IP address on which instance serial console should listen
+    # (string value)
+    #listen=127.0.0.1
+
+    # The address to which proxy clients (like nova-serialproxy)
+    # should connect (string value)
+    #proxyclient_address=127.0.0.1
+
+
+Enabling the service is enough to be functional for a single machine devstack.
+
+These config options are defined in `nova.console.serial
+<https://github.com/openstack/nova/blob/master/nova/console/serial.py#L33-L52>`_
+and `nova.cmd.serialproxy
+<https://github.com/openstack/nova/blob/master/nova/cmd/serialproxy.py#L26-L33>`_.
+
+For more information on OpenStack configuration see the `OpenStack
+Configuration Reference
+<http://docs.openstack.org/trunk/config-reference/content/list-of-compute-config-options.html>`_