With the new openstackdocstheme used, we can simplify conf.py.
Also, update our docs for it.
Note that Sphinx 1.6 needs latexmk for building, add it.
Sphinx 1.6 introduces a few new warnings, fix them so that the guides
built.
Change-Id: If2e431725eb54f8be79b9fa4bf9ede2089f321a5