Requests for non-existent records should return 404 errors

[torrin47]

Right now, links to details pages and metadata downloads for UUIDs that have no match in the EDG database first redirect to the edg-intranet server, then return a valid webpage that contains an error message within. Internal users trying to check for broken links, therefore, don't get a reliable and consistent 404 error that they could use for automatic testing, while external users end up with an error message saying that the edg-intranet server is inaccessible. Example: https://edg.epa.gov/metadata/catalog/search/resource/details.page?uuid=badUUID Instead:

• [x] If there is no match for the UUID in the database, the EDG should return a friendly File Not Found error with a 404 error code analogous to the standard EPA error page: https://www.epa.gov/badpage
• [x] EDG should no longer attempt to redirect any users to the edg-intranet server - this was intended to streamline viewing of restricted records which now comprise 0.3% of the EPA total and are being phased out.

[torrin47]

Also add message explaining IPv6 issue.