Add documentation for Cumulus Linux NCLU

The Cumulus Linux driver is supported but not documented.
Add it to the list of supported drivers.
Sort the list of supported drivers (it's getting long).
Provide basic example config.

Change-Id: I50c40dc3759389c4ab971e295014d3222f5da270
(cherry picked from commit 202e6bb)

Author: oneswig

doc/source/configuration.rst

@@ -148,6 +148,16 @@ for the Juniper Junos OS device::
     ngs_commit_timeout = <optional commit timeout (seconds)>
     ngs_commit_interval = <optional commit interval (seconds)>
 
+for a Cumulus Linux device::
+
+    [genericswitch:hostname-for-cumulus]
+    device_type = netmiko_cumulus
+    ip = <switch mgmt_ip address>
+    username = admin
+    password = password
+    secret = secret
+    ngs_mac_address = <switch mac address>
+
 Additionally the ``GenericSwitch`` mechanism driver needs to be enabled from
 the ml2 config file ``/etc/neutron/plugins/ml2/ml2_conf.ini``::
 

doc/source/supported-devices.rst

@@ -4,17 +4,18 @@ Supported Devices
 
 The following devices are supported by this plugin:
 
+* Arista EOS
+* Brocade ICX (FastIron)
 * Cisco 300-series switches
 * Cisco IOS switches
-* Huawei switches
-* OpenVSwitch
-* Arista EOS
+* Cumulus Linux (via NCLU)
 * Dell Force10
 * Dell PowerConnect
-* Brocade ICX (FastIron)
-* Ruijie switches
 * HPE 5900 Series switches
+* Huawei switches
 * Juniper Junos OS switches
+* OpenVSwitch
+* Ruijie switches
 
 This Mechanism Driver architecture allows easily to add more devices
 of any type.