updating sphinx documentation
updating sphinx documentation

* adding openstack theming (copied from keystone project theme)
* updating .gitignore to ignore generated API docs
* updated formatting in index.rst page
* updaed openstack/common/processutils.py to match hacking docstring
* updated docstrings to resolve sphinx warnings

Change-Id: Ie89afe20eeab1efd2daf440fc65ccdf90f723c51

poznyakandrey/oslo.service,citrix-openstack-build/oslo.service,eezhova/oslo.service,openstack/oslo.service