updated duration reporting

Updated Durations reporting so benchtool prints out sth like this:
19:40:35  INFO  Completed 10 INGEST action(s) executed in 1686 ms
19:40:35  INFO  Runtime excluding the threading overhead was 1686 ms
19:40:35  INFO  Runtime including the threading overhead was 2002 ms
19:40:35  INFO  Threading overhead was 316 ms
19:40:35  INFO  Complete benchmark took 6362 ms