Update docs template

To make things more consistent across all openstack projects, the
developer docs should be upgraded to the newer template used by
keystone and keystoneclient (and other projects).

I dropped in the necessary static files and themes, and updated
the config file to make the changes at build time.

Change-Id: I5a268cff3cd5af29ad712705d540b9d1d6667d56
Partial-Bug: #1331304
Merge "Update docs template"