[doc] Add Rubick arhitecture, rules engine docs stubs

Add Rubick architecture doc
Add rules engine doc stub
Rename arhictecture_model to openstack_architecture_model for clarity

doc/openstack_architecture_model.rst

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+=======================
+ARCHITECTURE DATA MODEL
+=======================
+
+Overview
+--------
+
+We want to introduce unified data structure which contains all information
+necessary to inspect, analyze, describe and visualize OpenStack architecture.
+
+This Architecture data model could be consumed and processed by configuration
+analysis and diagnostics tool (**Dark Knight**).
+
+Arhictecture data model must include all information necessary to deployment
+systems (e.g. **Fuel** or **TripleO**). We will implement simple conversion
+tools which will allow to configure these deployment systems and effectively
+support 'portable' clouds.
+
+This model could be reused by Rally project to compare benchmarking results for
+different architectures.
+
+The model can be used to inspect existing clouds for subsequent upgrade.
+
+The model suits as base for questionaire to assess existing installations for
+support contract pricing purposes.
+
+The model could be used to perform automated/guided hardening of OpenStack
+architecture and configuration.
+
+Data Format
+-----------
+
+This section proposes data model format which allows to describe an OpenStack
+installation. The model includes data regarding physical infrastructure, logical
+topology of services and mapping between the two.
+
+Architecture data model could be serialized as JSON or YaML document of the
+following format::
+
+    openstack
+        nodes
+            node1
+                -param1: value
+                -param2: value
+        services
+            nova
+                configuration
+                    -param1: value
+                    -param2: value

doc/service_architecture.rst

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+===================
+RUBICK ARCHITECTURE
+===================
+
+.. image:: images/service_architecture.png