Refactoring on the operators: negation is now being handled globally

Other minors changes were also made, including adding the prefix `m_'
to all the members of the class.

src/operators/validate_url_encoding.cc

@@ -115,10 +115,6 @@ bool ValidateUrlEncoding::evaluate(Transaction *transaction,
             break;
     }
 
-    if (negation) {
-        return !res;
-    }
-
     return res;
 }