Integrate MutationMgr/StreamReader with latest stream library

- Use protobuf message format being sent by stream library in
stream reader(stream_reader.go)
- Copy the actual mutation data in MutationKeys/MutationMeta structs
to allow underlying protobuf library to reuse its structs
- Change mutation queue to handle new structs(mutation_queue_atomic.go)
- Change mutation manager to use latest index and partition definition
structs

Change-Id: I346a4b04eb4618f47fbf3ba149ffea994acdf286
Reviewed-on: http://review.couchbase.org/38302
Reviewed-by: John Liang <johliang00@gmail.com>
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Tested-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>