EXAMPLES: add a trivial config for quick testing

EXAMPLES: add a trivial config for quick testing

This config was taken from the example provided in the dpbench project.
It uses minimalistic keywords and is trivial to setup and adapt on any
test machine for a quick test. It can be convenient when comparing
different server platforms to pick the one delivering the best
performance in various dimensions (conn rate, req rate, ssl rate,
bit rate). It uses a single listener (optionally a second one with
SSL), a single server, power-of-two-choices (random(2)) algorithm,
and no privileged directive.