Add a silent option

This pull request contains a silent option to the testharness. It allows for bots to be run without printing all the output to the console. The only output is dots to stderr as each round progresses, and the final result (two values) to stdout.

The main benefit of this is that it allows for running the testharness from a script to do tests and record these tests by capturing stdout.

(Tested on osx with mono)