Add Release Notes and Architecture Docs

Add release note for Pike and architecture documentation
and diagram.

Change-Id: Ia5756ed7acf176f3910dfe2436da8186467377c8
Signed-off-by: zhipengh <huangzhipeng@huawei.com>

doc/source/architecture.rst

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+Cyborg architecture
+====================
+
+Cyborg design can be described by following diagram:
+
+.. image:: images/cyborg-architecture.png
+    :width: 700 px
+    :scale: 99 %
+    :align: left
+
+**cyborg-api** - cyborg-api is a cyborg service that provides **REST API**
+interface for the Cyborg project. It supports POST/PUT/DELETE/GET operations
+and interacts with cyborg-agent and cyborg-db via cyborg-conductor.
+
+**cyborg-conductor** - cyborg-conductor is a cyborg service that coordinates
+interaction, DB access between cyborg-api and cyborg-agent.
+
+**cyborg-agent** - cyborg-agent is a cyborg service that is responsible for
+interaction with accelerator backends via the Cyborg Driver. For now the only
+implementation in play is the Cyborg generic Driver. It will also handle the
+communication with the Nova placement service. Cyborg-Agent will also write to
+a local cache for local accelerator events.
+
+**cyborg-generic-driver** - cyborg-generic-driver is a general multipurpose
+driver with the common set of capabilities that any accelerators will have.

releasenotes/notes/basic-framework-28d6b42d9bf684af.yaml

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+---
+features:
+  - |
+    The Cyborg framework consists of three core services:Api, Conductor
+    and Agent.
+    Cyborg Api supports GET/POST/PUT/DELETE operations for accelerators.
+    Cyborg conductor is responsible for handling all API requests that come in
+    via the API service.
+    Cyborg Agent is responsible for all the Nova Cyborg interaction.