add initial release notes

Change-Id: I6eb9d874335b9caac14c28660bee81c3289cea8f

releasenotes/notes/configurable-data-collector-e247aadbffb85243.yaml

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+---
+features:
+  - >
+    [`bug 1480333 <https://bugs.launchpad.net/ceilometer/+bug/1480333>`_]
+    Support ability to configure collector to capture events or meters mutally
+    exclusively, rather than capturing both always.
+other:
+  - >
+    Configure individual dispatchers by specifying meter_dispatchers and
+    event_dispatchers in configuration file.

releasenotes/notes/gnocchi-cache-1d8025dfc954f281.yaml

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+---
+features:
+  - >
+    Support resource caching in Gnocchi dispatcher to improve write
+    performance to avoid additional queries.
+other:
+  - >
+    A dogpile.cache supported backend is required to enable cache. Additional
+    configuration `options <http://docs.openstack.org/developer/oslo.cache/opts.html#cache>`_
+    are also required.

releasenotes/notes/remove-alarms-4df3cdb4f1fb5faa.yaml

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+---
+features:
+  - >
+    Ceilometer alarms code is now fully removed from code base.
+    Equivalent functionality is handled by Aodh.  

releasenotes/notes/remove-eventlet-6738321434b60c78.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - >
+    Remove eventlet from Ceilometer in favour of threaded approach

releasenotes/notes/sql-query-optimisation-ebb2233f7a9b5d06.yaml

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+---
+fixes:
+  - >
+    [`bug 1506738 <https://bugs.launchpad.net/ceilometer/+bug/1506738>`_]
+    [`bug 1509677 <https://bugs.launchpad.net/ceilometer/+bug/1509677>`_]
+    Optimise SQL backend queries to minimise query load

releasenotes/notes/support-snmp-cpu-util-5c1c7afb713c1acd.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - >
+    [`bug 1513731 <https://bugs.launchpad.net/ceilometer/+bug/1513731>`_]
+    Add support for hardware cpu_util in snmp.yaml

releasenotes/notes/thread-safe-matching-4a635fc4965c5d4c.yaml

@@ -0,0 +1,6 @@
+---
+critical:
+  - >
+    [`bug 1519767 <https://bugs.launchpad.net/ceilometer/+bug/1519767>`_]
+    fnmatch functionality in python <= 2.7.9 is not threadsafe. this issue and 
+    its potential race conditions are now patched.