docs: Add reference to server configuration section

BuildGrid/buildgrid#147

docs/source/reference_server_config.rst

-.. _parser:
 
-Server configuration reference
-==============================
+.. _server-configuration:
 
-BuildGrid's server configuration. To be used with::
+Server configuration
+====================
 
-  bgd server start server.conf
+BuildGrid's server YAML configuration format details.
+
+.. hint::
+
+   In order to spin-up a server instance using a given ``server.conf``
+   configuration file, run:
+
+   .. code-block:: sh
+
+      bgd server start server.conf
+
+   Please refer to the :ref:`CLI reference section <invoking-bgd-server>` for
+   command line interface details.
+
+
+.. _server-config-reference:
+
+Reference configuration
+-----------------------
+
+Below is an example of the full configuration reference:
+
+.. literalinclude:: ../../buildgrid/_app/settings/reference.yml
+   :language: yaml
+
+
+.. _server-config-parser:
+
+Parser API
+----------
+
+The tagged YAML nodes in the :ref:`reference above <server-config-reference>`
+are handled by the YAML parser using the following set of objects:
 
 .. automodule:: buildgrid._app.settings.parser
     :members: