driver: fixed reaction on worker error
driver: more accurate measurment of worker first processing time
chunk: added queue id (and read/write ids) into all log output
queue: fixed iteration over unacked entries (replay_iterator)
queue: added queue id into all log output
queue: more precise timeout checking and ack-wait-timeouts and timeout-check-period configurables
queue: true bulk ack, writes meta once per call
queue: guard for over-acking
queue: a bit more logging (write meta, popping)
queue-pull: command line option to set request size
data_array: iterator object
driver: more gradual rate speed up