doc: Modify the master file to a single ToC.

- Consolidates the links to the sections in a single table of contents.
- Adds the documentation's version number.
- Adds a link to the project's Wiki.

Change-Id: I762d30ce8cbf518df8a28e428e94a2f9a3c7085d
Signed-off-by: Rodrigo Caballero <rodrigo.caballero.abraham@intel.com>

doc/index.rst

@@ -4,8 +4,10 @@
 Zephyr Project Documentation
 ############################
 
-Getting Started
-***************
+Welcome to the Zephyr Project's documentation version |version|!
+
+Sections
+********
 
 .. toctree::
    :maxdepth: 1
@@ -15,38 +17,21 @@ Getting Started
    kernel/kernel.rst
    drivers/drivers.rst
    subsystems/subsystems.rst
-
-Developer Guides
-****************
-
-.. toctree::
-   :maxdepth: 1
-
    contribute/code.rst
    reference/kbuild/kbuild.rst
    application/application.rst
    api/api.rst
    collaboration/collaboration
-
-Reference Guides
-****************
-
-.. toctree::
-   :maxdepth: 1
-
    reference/kconfig/index.rst
-
-Supported Boards
-****************
-
-.. toctree::
-   :maxdepth: 2
-
    board/board.rst
 
+You can find further information on the `Zephyr Project Wiki`_.
+
 Indices and Tables
 ******************
 
 * :ref:`genindex`
 
 * :ref:`search`
+
+.. _Zephyr Project Wiki: https://wiki.zephyrproject.org/view/Main_Page