Add a common label to all resources on `kube apply'

Add "template=<ID>" label to all resources with a Labels field declared
during the Template to Config transformation, so these resources can be
later referenced as a group.
- Service.Labels
- Pod.Labels
- ReplicationController.Labels
- ReplicationController.DesiredState.PodTemplate.Labels
Add tests for config AddConfigLabels() and mergeMaps() functions