pypyr.log.logger.set_root_logger(log_level, log_path) call moved from pipelinerunner.main() to cli.main()

this has the side-effect that pipelinerunner.main() signature has changed, with log_level and log_path removed. API consumers should update.

Reason being API consumers should set their own log handlers, since handler configuration should be the prerogative of the calling application, not the invoked library.

Re #172, #173