refactoring: move the message logger setup out of main()

Eventually we will want to use this code in other sample applications,
so let's move the logger configuration code to a separate function.

There's a bit of ugly hacking in this current implementation because
I've added variable members to logging.logger.  These are actaully
config-once variables that convey the logging directory and filename.
I did not want to add more names to the global namespace, so I hacked
a temporary solution in which logging.logger is acts as a conveyor and
private namespace.  We'll get that cleaned up as we do more refactoring.