sourceResource.language searches in the API behave oddly

Reported by Twitter: http://twitter.com/recology_/status/534470175626518528

• Queries using the argument @sourceResource.language.iso639@ don't return results. This appears to be an incorrect property name in the documentation, but the Elasticsearch schema probably needs to be fixed as well)

• Queries using the argument @sourceResource.language.name@ seems to be case sensitive (e.g. "German" returns results, but "german" does not)