RFE: a hook to manipulate tenant deployment-configuration before sending to OSO

[fche]

@aslakknutsen suggested that an alternative to fabric8-services/fabric8-tenant-jenkins#57 (and several others along that line) could be the adjustment of original DCs on a per-tenant basis.

We may need to add routes, maybe a container to the pod(s); we don't know yet the entirety. So it'd be great to have a facility that lets us modify DCs en-route to OSO, but without too much hard-coding within f8 proper.