Add proxy deposit and transfers of ownership (from ScholarSphere).

**DO NOT MERGE** This is a WIP, with 12 feature specs still failing.

I'm looking for:

1. Someone to do a preliminary review of this code so I can make major
   corrections before submitting the mergeable PR.
2. A kind soul who may be able to take a quick look at the failing specs
   and give me a second set of eyes re: the 12 spec failures. The specs
   that are failing are spec/features/{collection,proxy,ownership_transfer}_spec.rb
   and my best guess about the failures is that they're related to the
   select2-rails gem.

Anyone up for this?  I'd be much obliged for either.  Check out Travis to
see the failures.