Host a devstack.org redirect on static

This provides a hollow "devstack.org" vhost as a permanent redirect
to the docs.openstack.org/developer/devstack site. It also aliases
*.devstack.org to the same vhost.

Change-Id: Ib96e4d4e21bbdd961eb32529c66acf750d79bec5
Merge "Host a devstack.org redirect on static"