34404 create rev from json

Allow the creation of CDTDocumentRevisions for use with remote data sources
From I understood talking to the MobileFirst guys working on Unify, this factory method is used to create a CDTDocumentRevision from a remote couched/cloudant without persisting to disk. The draw back of using this either class is that unify could attempt to save a modified document to our datastore causing errors. 

I think a way we could fix this is be creating CDTRemoteDocumentRevision which wouldn't be able to be passed into CDTMutableDocumentRevision method calls