Add callback function option for the Client Query API

[ibrodkin]

Add Chronolog client API that allows the Client to provide a callback function that takes an chronolog Event record as a parameter.
The callback function would be executed by the client API on every event record within the query response set without the need to transform and copy the internal response set of StoryChunks into the std::vectorchronolog::Event & that is time and memory consuming in case of the large number of records.