Implement "backpressure" support on query receiver to avoid OOM

The current implementation is capable of reaching OOM if a large stream is being received from the query engine and the application-level processing is not fast enough to keep up.

This is a request to implement "backpressure" (for lack of a better word) within the client to prevent over-use of memory.  According to Marco Greco: all the SDK has to do is decide that it already has too much memory in use and delay a recv() until memory is manegeable. the server will slow down just because the client is not reading