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/site/local.bro

@@ -11,6 +11,13 @@
 # Load the scan detection script.
 @load misc/scan
 
+# Log some information about web applications being used by users 
+# on your network.
+@load misc/app-metrics
+
+# Detect traceroute being run on the network.  
+@load misc/detect-traceroute
+
 # Generate notices when vulnerable versions of software are discovered.
 # The default is to only monitor software found in the address space defined
 # as "local".  Refer to the software framework's documentation for more