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/unconditional_match.cc

@@ -22,10 +22,6 @@ bool UnconditionalMatch::evaluate(Transaction *transaction,
     const std::string &input) {
     bool contains = true;
 
-    if (negation) {
-        return !contains;
-    }
-
     return contains;
 }