Add release notes template and improve format

Adds a new template from which release notes will be created.
This allows us to maintain a structred format for future
release notes. Also makes some changes to the way release
notes are formatted to ensure clarity.

Change-Id: I489f44bf214dc0bf47e486f9969f428d8618de40

doc/source/release_notes_template.rst

@@ -0,0 +1,112 @@
+.. _release_notes_<VERSION>
+
+===========================
+<release version goes here>
+===========================
+
+Summary
+=======
+
+The <VERSION> OpenStack Charm release includes updates for the following charms:
+
+TODO: ensure these lists are accurate and up-to-date
+
+Supported Charms
+~~~~~~~~~~~~~~~~
+
+* aodh
+* barbican
+* ceilometer
+* ceilometer-agent
+* ceph-fs
+* ceph-mon
+* ceph-osd
+* ceph-proxy
+* ceph-radosgw
+* cinder
+* cinder-backup
+* cinder-ceph
+* designate
+* designate-bind
+* glance
+* gnocchi
+* hacluster
+* heat
+* keystone
+* keystone-ldap
+* lxd
+* manila
+* manila-generic
+* neutron-api
+* neutron-api-odl
+* neutron-openvswitch
+* neutron-gateway
+* nova-cloud-controller
+* nova-compute
+* odl-controller
+* openstack-dashboard
+* openvswitch-odl
+* percona-cluster
+* rabbitmq-server
+* swift-proxy
+* swift-storage
+
+Pre-Release Charms
+~~~~~~~~~~~~~~~~~~
+* 
+
+Deprecated Charms
+~~~~~~~~~~~~~~~~~~
+* ceph
+
+New Charm Features
+==================
+
+Feature Title
+~~~~~~~~~~~~~
+
+Feature description.
+
+Upgrading charms
+================
+
+Please ensure that the keystone charm is upgraded first.
+
+To upgrade an existing deployment to the latest charm version simply use the
+'upgrade-charm' command:
+
+.. code:: bash
+
+    juju upgrade-charm keystone
+
+New Bundle Features
+===================
+
+Bundle Feature Title
+~~~~~~~~~~~~~~~~~~~~
+
+Bundle feature description goes here.
+
+Deprecation Notices
+===================
+
+Deprecation details go here.
+
+Known Issues
+============
+
+Issue title
+~~~~~~~~~~~
+
+Issue description goes here.
+
+Bugs Fixed
+==========
+
+For the full list of bugs resolved for the <VERSION> release please refer to
+https://launchpad.net/openstack-charms/+milestone/<VERSION>
+
+Next Release Info
+=================
+Name, Date etc
+