Validation Report

This is now out-of-date: please see "Validation Report (revised)" below

Validation Report
  - Update IndexService to get missing field data from Solr
  - Model, controller, routes, and basic views for ValidationReport
  - Rake task to index sample invalid aggregation into Solr
Can you get the desired behavior by overriding [`Blacklight::UrlHelperBehavior#url_for_document`](https://github.com/projectblacklight/blacklight/blob/master/app/helpers/blacklight/url_helper_behavior.rb#L10-L20) instead?