Change validator response to add admin.valid_after_enrich property

After discussing with @rudeamy and @migbot it sounds like we really
need a way to generate a report of invalid records rather than
preventing them from being ingested at all. After discussion
on IRC, Miguel and I agreed that the best way to do this would
be to add a sub-property to the 'admin' property in each record,
against which we could generate a view. Invalid records also no
longer throw an HTTP error when sent to this endpoint.

This could also be the basis for a mechanism to filter out invalid
records from API queries at some point in the future.