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/http/detect-sqli.bro

@@ -28,7 +28,7 @@ export {
 	## Defines the threshold that determines if an SQL injection attack
 	## is ongoing based on the number of requests that appear to be SQL
 	## injection attacks.
-	const sqli_requests_threshold = 50 &redef;
+	const sqli_requests_threshold: double = 50.0 &redef;
 
 	## Interval at which to watch for the
 	## :bro:id:`HTTP::sqli_requests_threshold` variable to be crossed.
@@ -64,11 +64,12 @@ event bro_init() &priority=3
 	# determine when it looks like an actual attack and how to respond when
 	# thresholds are crossed.
 	local r1: SumStats::Reducer = [$stream="http.sqli.attacker", $apply=set(SumStats::SUM), $samples=collect_SQLi_samples];
-	SumStats::create([$epoch=sqli_requests_interval,
+	SumStats::create([$name="detect-sqli-attackers",
+	                  $epoch=sqli_requests_interval,
 	                  $reducers=set(r1),
 	                  $threshold_val(key: SumStats::Key, result: SumStats::Result) =
 	                  	{
-	                  	return double_to_count(result["http.sqli.attacker"]$sum);
+	                  	return result["http.sqli.attacker"]$sum;
 	                  	},
 	                  $threshold=sqli_requests_threshold,
 	                  $threshold_crossed(key: SumStats::Key, result: SumStats::Result) =
@@ -82,11 +83,12 @@ event bro_init() &priority=3
 	                  	}]);
 
 	local r2: SumStats::Reducer = [$stream="http.sqli.victim", $apply=set(SumStats::SUM), $samples=collect_SQLi_samples];
-	SumStats::create([$epoch=sqli_requests_interval,
+	SumStats::create([$name="detect-sqli-victims",
+	                  $epoch=sqli_requests_interval,
 	                  $reducers=set(r2),
 	                  $threshold_val(key: SumStats::Key, result: SumStats::Result) =
 	                  	{
-	                  	return double_to_count(result["http.sqli.victim"]$sum);
+	                  	return result["http.sqli.victim"]$sum;
 	                  	},
 	                  $threshold=sqli_requests_threshold,
 	                  $threshold_crossed(key: SumStats::Key, result: SumStats::Result) =