Feature/add crud datastream

This pull request got a bit manky, sorry about that.  

A bunch of the changes that were made here got axed in favor of making those changes in our DRS application.  But there are two left: 

1.  Updates the update_metadata_from_upload_screen method to take a generic_file as an argument.  This makes it a little clearer what's going on from the DRS sufia application. 

2.  Rough beginnings of a support for our oaidc datastream that the core objects wiki page indicated we should be supporting.  This isn't the right branch for it really so I figure if it gets merged into develop the rest of the work that needs to happen can do so in the right place.