drop 'Request' suffix requirement for request name

Session.request() will handle appending 'Request' to the 'name'
parameter for the underlying blpapi-node API.
support partial responses

This change introduces error-first style callbacks for requests.  A
third parameter for the callback indicates whether it is the final
invocation of the callback for a given request.
properly append 'Request' everywhere
Merge remote-tracking branch 'eric/api_abstraction' into qndirty-m
Handle partial responses