Add some items to the release notes

Change-Id: I75d56e5d987c0564e75f9721ee4aae69069ed330

releasenotes/notes/availability-zone-support-8e66f55e46b7ef9a.yaml

@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    CLI support for availability zones.
+
+    * The ``availability-zone-list`` command provides a list of
+      availability zones.
+    * The ``net-create`` and ``router-create`` commands include a
+      ``--availability-zone-hint`` option.
+    * The ``agent-list`` command output includes availability zones.

releasenotes/notes/docs-improvements-17e31babe38e2962.yaml

@@ -0,0 +1,5 @@
+---
+other:
+  - |
+    Addition of CLI user documentation including output filters, extra
+    options, and operation using os-client-config.

releasenotes/notes/drop-nuage-commands-df10aab6ccd77ed2.yaml

@@ -0,0 +1,3 @@
+---
+upgrade:
+  - Remove Nuage-specific commands.