Use oslo.sphinx and remove local copy of doc theme

Use the new oslo.sphinx version of the OpenStack doc
theme instead of copying it into this repo.

blueprint oslo.sphinx

Change-Id: I0bd91f7bb43f97b99051fed65b75fc05d5149cc8
Include docstrings in published docs

Change-Id: Icdfb0535b26162d39c3af683b7729b5e834d89b9