Add regex MetricFilter to GraphiteSink

Today all registered metric sources are reported to GraphiteSink with no filtering mechanism, although the codahale project does support it.

GraphiteReporter (ScheduledReporter) from the codahale project requires you implement and supply the MetricFilter interface (there is only a single implementation by default in the codahale project, MetricFilter.ALL).

Propose to add an additional regex config to match and filter metrics to the GraphiteSink