Improve handling of large responses in nasty client

[jbearer]

Some of the responses to queries like payload queries and range queries can be up to a few megabytes. This change prevents distracting spurious warnings and errors for such responses.

This PR:

• increases the HTTP client timeout to allow plenty of time to stream the response over the network
• only counts queries as slow if it takes longer than 1s to receive a response header -- the time it takes to stream the response does not count toward slow warnings, as this time is not taking computational resources on the server