add direct links to resources based on DOG analysis of known repositories

[dietervu]

Situation: non-CMDI metadata (from Dublin Core or DataCite) with only a link to the landing page.

On access of the VLO page. probe via the DOG API in the background if the landing page is pointing to a repository that is known to the DOG. If so, issue a fetch command and add the direct links to the resources in the VLO, so that e.g. processing with the Switchboard becomes available.

This scenario also requires performance/stress testing of the DOG API.