Validaiton Report

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
I think it's probably worth reviewing what would need to happen for this to be implemented in Blacklight, and how tightly coupled it would be to Solr. It's also worth thinking about this in relation to the Blacklight abstraction work.