API updates for metrics framework.

- Removed default logging.  Now a function is available for the new
  $period_finished filter field to get the same behavior for logging
  named Metrics::write_log.

- Added index rollups for getting multiple metrics result values
  as the same time.

scripts/policy/frameworks/metrics/ssl-example.bro

@@ -10,11 +10,10 @@ event bro_init()
 	{
 	Metrics::add_filter("ssl.by_servername", 
 		[$name="no-google-ssl-servers",
+		 $every=10secs, $measure=set(Metrics::SUM),
 		 $pred(index: Metrics::Index, data: Metrics::DataPoint) = { 
 		    return (/google\.com$/ !in index$str); 
-		 },
-		 $break_interval=10secs
-		]);
+		 }]);
 	}
 
 event SSL::log_ssl(rec: SSL::Info)