Add strategy template doc

Developer should provide a detailled documentation about his strategy
algorithm to make it even easier to use by a Watcher end user.
I propose in this changeset a template for strategy documentation.
you will find also a example with basic consolidation strategy.

Change-Id: I66da1a33b87a94b508dd23ac7dce4cae6f4e068b

doc/source/strategies/strategy-template.rst

@@ -0,0 +1,109 @@
+=============
+Strategy name
+=============
+
+Synopsis
+--------
+
+**display name**:
+
+**goal**:
+
+Add here a complete description of your strategy
+
+Requirements
+------------
+
+Metrics
+*******
+
+Write here the list of metrics required by your strategy algorithm (in the form
+ of a table). If these metrics requires specific Telemetry plugin or other
+ additional software, please explain here how to deploy them (and add link to
+ dedicated installation guide).
+
+Example:
+
+======================= ============ ======= =======
+metric                  service name plugins comment
+======================= ============ ======= =======
+compute.node.*          ceilometer_  none    one point every 60s
+vm.cpu.utilization_perc monasca_     none
+power                   ceilometer_  kwapi_  one point every 60s
+======================= ============ ======= =======
+
+
+.. _ceilometer: http://docs.openstack.org/admin-guide/telemetry-measurements.html#openstack-compute
+.. _monasca: https://github.com/openstack/monasca-agent/blob/master/docs/Libvirt.md
+.. _kwapi: https://kwapi.readthedocs.io/en/latest/index.html
+
+
+Cluster data model
+******************
+
+Default Watcher's cluster data model.
+
+or
+
+If your strategy implementation requires a new cluster data model, please
+ describe it in this section, with a link to model plugin's installation guide.
+
+Actions
+*******
+
+Default Watcher's actions.
+
+or
+
+If your strategy implementation requires new actions, add the list of Action
+ plugins here (in the form of a table) with a link to the plugin's installation
+ procedure.
+
+======== =================
+action   description
+======== =================
+action1_ This action1 ...
+action2_ This action2 ...
+======== =================
+
+.. _action1 : https://github.com/myrepo/watcher/plugins/action1
+.. _action2 : https://github.com/myrepo/watcher/plugins/action2
+
+Planner
+*******
+
+Default Watcher's planner.
+
+or
+
+If your strategy requires also a new planner to schedule built actions in time,
+ please describe it in this section, with a link to planner plugin's
+ installation guide.
+
+Configuration
+-------------
+
+If your strategy use configurable parameters, explain here how to tune them.
+
+
+Efficacy Indicator
+------------------
+
+Add here the Efficacy indicator computed by your strategy.
+
+How to use it ?
+---------------
+
+.. code-block:: shell
+
+    $ Write the command line to create an audit with your strategy.
+
+External Links
+--------------
+
+If you have written papers, blog articles .... about your strategy into Watcher,
+ or if your strategy is based from external publication(s), please add HTTP
+ links and references in this section.
+
+- `link1 <http://www.link1.papers.com>`_
+- `link2 <http://www.link2.papers.com>`_