Address bug#244
The merge request is to address the issue of reference to a VNFD from within a NSD. Today that reference is relative to an instance of a VNFD that is declared along with a NSD. However, a VNFD (or a PNFD) can be on boarded separately from a NSD.
This change is remove declaration of a VNFD (and PNFD) within a NSD, and to refer to them in absolute terms.