Large update for the SumStats framework.

- On-demand access to sumstats results through "return from"
   functions named SumStats::request and Sumstats::request_key.
   Both functions are tested in standalone and clustered modes.

 - $name field has returned to SumStats which simplifies cluster
   code and makes the on-demand access stuff possible.

 - Clustered results can only be collected for 1 minute from their
   time of creation now instead of time of last read.

 - Thresholds use doubles instead of counts everywhere now.

 - Calculation dependency resolution occurs at start up time now
   instead of doing it at observation time which provide a minor
   cpu performance improvement.  A new plugin registration mechanism
   was created to support this change.

 - AppStats now has a minimal doc string and is broken into hook-based
   plugins.

 - AppStats and traceroute detection added to local.bro

scripts/policy/protocols/ftp/detect-bruteforcing.bro

@@ -17,7 +17,7 @@ export {
 
 	## How many rejected usernames or passwords are required before being
 	## considered to be bruteforcing.
-	const bruteforce_threshold = 20 &redef;
+	const bruteforce_threshold: double = 20 &redef;
 
 	## The time period in which the threshold needs to be crossed before
 	## being reset.
@@ -28,11 +28,12 @@ export {
 event bro_init()
 	{
 	local r1: SumStats::Reducer = [$stream="ftp.failed_auth", $apply=set(SumStats::UNIQUE)];
-	SumStats::create([$epoch=bruteforce_measurement_interval,
+	SumStats::create([$name="ftp-detect-bruteforcing",
+	                  $epoch=bruteforce_measurement_interval,
 	                  $reducers=set(r1),
 	                  $threshold_val(key: SumStats::Key, result: SumStats::Result) =
 	                  	{
-	                  	return result["ftp.failed_auth"]$num;
+	                  	return result["ftp.failed_auth"]$num+0.0;
 	                  	},
 	                  $threshold=bruteforce_threshold,
 	                  $threshold_crossed(key: SumStats::Key, result: SumStats::Result) =