Add build job for config reference

For Havana, we'll be introducing a configuration reference.

https://wiki.openstack.org/wiki/Blueprint-restructure-documentation

This patch adds a build job for the new document.

patchset2 rebases to master

Change-Id: Ia00831cbcf69444f591837b08c750bfdf4746d03
bp:restructure-documentation
Merge "Add build job for config reference"