Add parameters to --non-interactive mode of harness

A minimally invasive change to have a fixed number of measurements and a give problem size used for benchmarking.

Note, I had problems with ARGV.index() not working, so, I chose to give --non-interactive two optional parameters instead.

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Rename and simplify non-interactive running of a benchmark.
Merge branch 'simpler-harness'