Efficient object versioning using rsync/rdiff-style aglorithm

Swift supports object versioning symantics whereby multiple versions of objects can be uploaded to a single object name. Presently, each version of the object must uploaded in it's entirety. When object versioning is used, typically the objects are slightly variant from previous versions of the object. It should be possible for a swift user to simply upload an rsync-style delta of a file. Once the delta is received by Swift, it is applied to the previous version of the object and the finalized object is stored and replicated across object nodes as usual.