implement status command for the gitlab-ci-multi-runner
As most services we need a status command that should return information about current running service.
If the service is not running it should return non zero code.
Also this would be a good opportunity to say if the configuration from disc (config.taml) does match the loaded configuration.
Status command should also output some information regarding what runners are running and if they have any jobs, so we would know if is safe to restart the service.
