code: public boolean isApplicable(Class<? extends T> targetType) {
          Class<? extends T> applicable = Functions.getTypeParameter(clazz,getP(),0);
          return applicable.isAssignableFrom(targetType);
      }
docs: Returns true if this property type is applicable to the
  given target type.
  
  <p>
  The default implementation of this method checks if the given node type is assignable
  according to the parameterization, but subtypes can extend this to change this behavior.
  
  @return
  true to indicate applicable, in which case the property will be
  displayed in the configuration screen of the target, for example.