Change GoMetricsWorker to use the new way of specifying configs (involved using GoWorkerMixin and GoWorkerConfigMixin)
Mention that GoMetricsWorkerConfig's 'metrics_interval' is in seconds
Merge branch 'develop' into feature/issue-755-config-for-gometricsworker
Merge branch 'feature/issue-755-config-for-gometricsworker' into develop