Simplify combo.css

The combo.css file was very complicated and difficult to
edit, pulled out unused sections so it's easier to
maintain and compatible with our s header.

Change-Id: I23b223d3c5af7db49da9ede47f69ef9792106888
Reviewed-on: https://review.openstack.org/31141
Approved: Dan Prince <dprince@redhat.com>
Reviewed-by: Dan Prince <dprince@redhat.com>
Tested-by: Jenkins