Uses latest fcrepo-snapshot build (3.0.0-RC1-SNAPSHOT) of metrics, which...

... addresses

https://github.com/codahale/metrics/issues/359
and, in turn,
	https://github.com/codahale/metrics/issues/334

Removes MetricsService from fcrepo-kernel in favor of RegistryService from
fcrepo-metrics (not sure why we had this duplication to begin with)