Adds starting point for Architecture and Design Guide

The areas that still need work are:
- needs double-checking for tables
- see http://docs.openstack.org/arc/OpenStackArchitectureDesignGuide.epub
  for intended structure

Co-Authored-By: Nick Chase <nchase@mirantis.com>
Co-Authored-By: Beth Cohen <beth.cohen@verizon.com>
Co-Authored-By: Sean Collins <sean_collins2@cable.comcast.com>
Co-Authored-By: Steve Gordon <sgordon@redhat.com>
Co-Authored-By: Sebastian Gutierrez <segutier@redhat.com>
Co-Authored-By: Kevin Jackson <Kevin.Jackson@rackspace.co.uk>
Co-Authored-By: Scott Lowe <slowe@vmware.com>
Co-Authored-By: Maish Saidel-Keesing <msaidelk@cisco.com>
Co-Authored-By: Alexandra Settle <alexandra.settle@rackspace.com>
Co-Authored-By: Vinny Valdez <vvaldez@redhat.com>
Co-Authored-By: Anthony Veiga <Anthony_Veiga@cable.comcast.com>
Co-Authored-By: Sean Winn <sean.winn@cloudscaling.com>

Change-Id: Ia0ca278cd5d2d0ee67b9b7528870c1a2a80fdadf
Merge "Adds starting point for Architecture and Design Guide"