Misc. doc/script/test cleanup.

- fixing some Metrics::add_data() call signatures
- slight refactors to cluster framework @if and adding a NONE NodeType for
  so local_node_type() will return that instead of just emitting an error
  when cluster mode isn't enabled
- `make restdoc` target now uses bro's bare-mode
- bro scripts generated from bifs now really only live in the build/src/base/
  directory and changed the DocSourcesList.cmake to dynamically figure out
  what bifs exist by looking in src/ instead of build/src/
- add some missing @load dependencies

scripts/base/frameworks/cluster/main.bro

@@ -10,6 +10,7 @@ export {
 	} &log;
 	
 	type NodeType: enum {
+		NONE,
 		CONTROL,
 		MANAGER,
 		PROXY,
@@ -54,8 +55,8 @@ export {
 	
 	## This function can be called at any time to determine what type of
 	## cluster node the current Bro instance is going to be acting as.
-	## :bro:id:`is_enabled` should be called first to find out if this is
-	## actually going to be a cluster node.
+	## If :bro:id:`Cluster::is_enabled` returns false, then
+	## :bro:enum:`Cluster::NONE` is returned.
 	global local_node_type: function(): NodeType;
 	
 	## This gives the value for the number of workers currently connected to,
@@ -81,7 +82,7 @@ function is_enabled(): bool
 
 function local_node_type(): NodeType
 	{
-	return nodes[node]$node_type;
+	return is_enabled() ? nodes[node]$node_type : NONE;
 	}