Resurrect violators/deadweight displays behind proper login

[lars-t-hansen]

The violators/deadweight displays are being removed in bug #679 but are meaningful for demo purposes and for admins / superusers, and should be made available to them. Not sure how this will work on the back-end as authorization is currently performed by sonalyzed and not nginx -- but maybe there's a general notion of "files that can be served to superusers" and they fit into that, something like "sonalyze serve filename" will serve the file if the proper credentials are presented. Then the dashboard can just make an HTTPS query to this service, there will be a credential challenge, and everything will be good.