Fixes for script auto-documentation.

- Fixing the parts of the `make restdoc` and `make doc` process that were
  broken by the last Bro script re-organization

- Generated documentation for Bro scripts derived from BiFs now use the
  original BiF source file as the "original source file" link

- Renaming of the internal POLICYDEST definition and other misc places that
  refer to "policy" scripts; that terminology doesn't make total sense now

- Added a documentation blacklist reminder test that will fail if there's
  scripts that are blacklisted from being documentated because they're still
  in progress

- Some minor Bro script changes to fix small @load dependency errors

Addresses #543

scripts/base/frameworks/metrics/http-example.bro

@@ -1,4 +1,4 @@
-@load frameworks/metrics
+@load base/frameworks/metrics
 
 redef enum Metrics::ID += {
 	HTTP_REQUESTS_BY_STATUS_CODE,
@@ -17,4 +17,4 @@ event HTTP::log_http(rec: HTTP::Info)
 		Metrics::add_data(HTTP_REQUESTS_BY_HOST, [$index=rec$host], 1);
 	if ( rec?$status_code )
 		Metrics::add_data(HTTP_REQUESTS_BY_STATUS_CODE, [$host=rec$id$orig_h, $index=fmt("%d", rec$status_code)], 1);
-	}
+	}