Remove double entries in history model
Remove double entries in history model

We were previously allowing multiple history items
that had the same properties. Now we only add
a new history item when it represents a different query
than the one before it.

[endlessm/eos-sdk#2981]

endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib