Add subway map to status page

Uses a table method similar to OpenStack's page. The code for
calculating the subway map tree is from
http://git.openstack.org/cgit/openstack-infra/config/tree/modules/openstack_project/files/zuul/status.js#n95

Added a sample JSON file that represents the dependency tree in
a very bad state.  All the images are grey because it's a bit old
and doesn't match the current JSON output in some areas, but it
does exercise quite a bit of the tree code.

Co-Authored-By: James E. Blair <jeblair@openstack.org>
Change-Id: I635ed101e5b1b168caa111ee61237cf1734813a1
Merge "Add subway map to status page"