Refining a view that includes an identity-based partition incorrectly filters all results

If a dataset is partitioned by a field's identity, and a RefinableView is created based on the identity field, nothing is returned by reading that view.

Some debugging revealed that in this case the PartitionKey was using a String, but the predicate filtering partitions was using a Long (the field's type), which of course won't satisfy the predicate since they two are never equal.

Not being deeply familiar with the code base, it's not clear to me what the best way to fix this is. However, the problem is exposed in the test in the attached diff, which can be applied to the 0.15.0 release tag.