34404 create rev from json

Allow creating CDTDocumentRevision objects for use with remote data sources

Create factory method which takes an NSDictionary and document URL.
- Reject dictionary if it contains any _prefixed values which are not couchdb properties
- Create any attachments as CDTRemoteAttachments defined in _attachments

The bugs likely to occur from this are using the API with NSDictionary objects containing incomplete data.

No I didn't, but looking at the doc it'll break compatibility with iOS 6 and OS X 10.8, I don't think we want to do that just yet.