Add -M (measure-mode), where master client only opens 1 connection per thread (to avoid client-side queuing delay).
1. Implemented --measure_* options to reasonably separate
configuration of measurement client (mutilate master) from
load generating clients (mutilate agents).  Use -C and
--measure_depth to approximate open-loop measurement control
(i.e. so long latency requests don't screw up the sample
population), and use -Q to ensure that you see minimal
client-side queuing delay.

2. Quickly documented agent "protocol".  Lots of improvement
to be had here...