Concept definition

template<typename EvaluatorType>
concept mgis::function::ST2toST2EvaluatorConcept = 
      (ST2toST21DEvaluatorConcept<EvaluatorType>) ||
      (ST2toST22DEvaluatorConcept<EvaluatorType>) ||
      (ST2toST23DEvaluatorConcept<EvaluatorType>)