Distinguish between query/txn opts and external opts

[JaceRockman]

Currently, we call both of them opts but they are used for different purposes and so we should update the naming of them to reflect this in some way. My initial thought was to keep the query/txn opts as opts but then use request-opts for the other one, but @dpetran pointed out that it's not necessarily the case that these functions will be called via a request. My next thought was a more generic name of external-opts.