Adding Files::register_for_mime_type() to associate a file analyzer

with a MIME type.

Whenever that MIME is detected, Bro will now automatically activate
the analyzer. The interface mimics how well-known ports are defined
for protocol analyzers.

This isn't actually used by any existing file analyzer (because we
don't have any yet that target a specific file format), but there's a
test making sure it works.

src/file_analysis/Component.cc

@@ -26,6 +26,6 @@ void Component::DoDescribe(ODesc* d) const
 	if ( factory )
 		{
 		d->Add("ANALYZER_");
-		d->Add(canon_name);
+		d->Add(CanonicalName());
 		}
 	}