Use openstack-hosted development config

The Kayobe development configuration has moved to
openstack/kayobe-config-dev. It was previously hosted at
stackhpc/dev-kayobe-config on Github.

This change updates the Zuul configuration and development documentation
to use the new location. It also uses a location for the kayobe source
code that works when kayobe is not the repository against which the code
review is targetted. This allows us to run kayobe jobs for
kayobe-config-dev changes.

Configuration for the seed VM and seed hypervisor development
environments is not yet supported by kayobe-config-dev, so the
documentation references a branch in my personal fork on Github.

Change-Id: I621324093b8dff0ac52a648539cd91bc12da4862