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/metrics/cluster.bro

@@ -5,6 +5,7 @@
 ##! transparently automated when running on a cluster.
 
 @load base/frameworks/cluster
+@load ./main
 
 module Metrics;
 
@@ -143,4 +144,4 @@ event Metrics::cluster_results(uid: string, id: ID, filter_name: string, data: M
 		}
 	}
 
-@endif
+@endif

scripts/base/frameworks/metrics/non-cluster.bro

@@ -1,3 +1,4 @@
+@load ./main
 
 module Metrics;