Fedora 4/datastreams

Here's a first-glance at what GenericFile looks like with all RDF properties and no descriptive metadata datastreams (excepting characterization).  Couple of things to note:

* the `desc_metadata__` solr field name prefix is gone
* order does not seem to be preserved for multiple property values
* date fields are coming back ISO8601
* outstanding issues with hydra-collections are noted in a separate commit