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

testing/btest/scripts/base/frameworks/metrics/basic.bro

@@ -0,0 +1,16 @@
+# @TEST-EXEC: bro %INPUT
+# @TEST-EXEC: btest-diff metrics.log
+
+redef enum Metrics::ID += {
+	TEST_METRIC,
+};
+
+event bro_init() &priority=5
+	{
+	Metrics::add_filter(TEST_METRIC, 
+		[$name="foo-bar",
+		 $break_interval=3secs]);
+	Metrics::add_data(TEST_METRIC, [$host=1.2.3.4], 3);
+	Metrics::add_data(TEST_METRIC, [$host=6.5.4.3], 2);
+	Metrics::add_data(TEST_METRIC, [$host=7.2.1.5], 1);
+	}