Remove ManagedRawFileStoreI in favor of callbacks

ManagedRawFileStoreI was not being used which meant that
closeCalled was never invoked and therefore the proxies
in `ManagedImportProcessI.uploaders` were never cleaned.
This led to `ObjectNotExistException` being thrown on a
second loading of `proc.getUploader(i)`. Rather than add
logic to create the correct subclass of RepoRawFileStoreI,
a callback interface has been added which can be used for
any implementation.

Previously known as:705b681
Add passing close test
Merge pull request #2610 from joshmoore/rebased/develop/fix-managed-rawfilestore

Fix managed rawfilestore (rebased onto develop)