* Changes behavior of Openvault::Pbcore::Ingester#ingest when the :replace_if_exists flag is set.
    Before, it would replace the Fedora object no matter what. Now it will only replace if the
    updated pbcore requires that that the object be reclassified as a different model.

* Refactors Openvault::Pbcore::DescriptionDocumentWrapper into a new class,
    Openvault::Pbcore::OpenvaultAssetUpdater. It's a little more semantic in class/method naming,
    and it gets cuts out some cruft.

* Gets rid of the ':ids' option for PbcoreDescDoc factory; use :all_ids instead.

* Gets rid of typo directory 'spec/models/datasream'.