New landing page structure

On the landing page there was no generic and basic info on ONAP yet,
 this has been added. A new architecture figure has been created.
ONAP documentation was made available from this main landing page as well.
The side bar of the landing page has also been changed.
 So far the section of the Release note have been made available
 from here, but now only the main doc titles are listed.

Issue-ID: DOC-351

Change-Id: I381c8e232438c51211a8a9303ea3589ebea4d4a4
Signed-off-by: Noemi Wagner <noemi.wagner@nokia.com>
diff --git a/docs/index.rst b/docs/index.rst
index d34a0eb..549850b 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -3,22 +3,48 @@
 
 .. _master_index:
 
-ONAP Documentation
-==================
+Open Network Automation Platform
+================================
 
-.. caution::
-   This version of documentation is created from the latest master branch of
-   source repositories, includes a proposed theme change, and is not a stable release.
-   To get the current stable release use one of the following
+Open Network Automation Platform (ONAP) is an open source project hosted by
+the Linux Foundation.
 
-   * http://docs.onap.org
-   * http://docs.onap.org/en/casablanca
-   * the selector on the bottom right and select casablanca
+ONAP provides a comprehensive platform for real-time, policy-driven service
+orchestration and automation. ONAP enables service providers and developers
+to rapidly automate the instantiation and configuration of physical and
+virtual network functions and to support complete life cycle management
+activities. By unifying the resources of open source members, ONAP enables
+the acceleration of the development of a vibrant ecosystem around a globally
+shared architecture and the implementation of network automation faster than
+any product could on its own.
+
+The ONAP Platform architecture is built on the highly efficient cooperation of
+Design-time Framework activities with the functions provided by the
+Run-time Framework. The Design-time Framework defines resources, services
+and products, creates and manages processes and policies, provides a single
+platform for deploying and defining instantiation management besides many
+other activities. The Run-time framework manages the full lifecycle of
+networks, services, resources, topology, orchestrates delivery, provides
+monitoring via analytics and controls activities for applications and
+virtual functions.
+
+ONAP platform activities are supported by the Microservices support
+system and by the ONAP Portal.
+
+The following figure presents the high-level architecture of ONAP:
+
+.. image:: media/ONAP-architecture-high-level.png
+    :width: 800px
+
+For more details, see :ref:`ONAP Documentation <onap-documentation>` (or alternatively you can also use the navigation bar on the left).
 
 .. toctree::
-   :maxdepth: 2
+   :maxdepth: 1
+   :hidden:
 
    release/index
    guides/onap-developer/index
    guides/onap-user/index
    guides/onap-provider/index
+
+