Add support for processing GetDataObjectsResponse chunks in client

Issue #75 (closed) added support in server for chunks in request. Now we need add the support in client for processing these chunks and re-assemble the data object.

Chunk messages are used when a data object is too large for the negotiated websocket message size limit.

From ETP Specs 9.3.7 For endpoints that receive these (chunk) messages, to correctly "reassemble" the data object (BLOB): use the blobId, and the messageId (which indicates the message sequence, because ETP (via WebSocket) guarantees messages to be delivered in order), and final (flag that indicates the last chunk that comprises a particular data object). Chunk messages for different data objects MUST NOT be interleaved within the context of one multipart message operation. If more than one data object must be sent using Chunk messages, the sender MUST finish sending each data object before sending the next one. To indicate the last Chunk message for one data object, the sender MUST set the final flag to true.