Adds new method for rule merge

IMPORTANT: SecDefaultAction specified on a child configuration will
overwrite the ones specified on the parent; Previously it was
concatenating.

src/operators/contains.h

@@ -36,7 +36,7 @@ class Contains : public Operator {
         : Operator("Contains", std::move(param)) { }
     bool evaluate(Transaction *transaction, RuleWithActions *rule,
         const std::string &str,
-        std::shared_ptr<RuleMessage> ruleMessage) override;
+        RuleMessage *ruleMessage) override;
 };
 
 }  // namespace operators