Provide generic 502 pages
Experience from the past years has shown 502 pages weren't provided
in a timely fashion for new services.
This change provides a generic 502 page with links for assistance.
It also provides a variant for status.nasqueron.org, as it isn't
possible there to recommend to check the status page.
Test Plan: Check links
Reviewed By: dereckson
Differential Revision: https://devcentral.nasqueron.org/D1969