Update batch operation protocol to include Batch message construct.

		// Perform Pin-based operations

		optional PinOperation pinOp = 8;

		// batch operation

		// This is included in the END_BATCH and END_BATCH_RESPONSE.

		optional Batch batch = 9;

	}

        // This is included in the END_BATCH and END_BATCH_RESPONSE.

        message Batch {

            // set by the client library in END_BATCH request message.

            // the total number of operations in the batch

            optional int32 count = 1;

            // set by the drive in END_BATCH_RESPONSE message.

            // If a batch is committed successfully, all sequence Ids of those

            // commands (PUT/DELETE) performed in the batch are

            // added in the END_BATCH_RESPONSE message.

            repeated int64 sequence = 2 [packed=true];

            // This field is set by the drive if a batch commit failed.

            // The first failed operation sequence in the batch is set as value.

            optional int64 failedSequence = 3;

	}

	//operation status