UIOutput converter attribute allows assigning a literal to specify the
converterId of the converter to be used or a ValueExpression evaluating to an
instance of Converter.
TLD doc only mentions the ValueExpression as allowed type and also the
Description does not mention the possibility to pass the converterId.
The same is missing for validator attributes on input components - TLD doc only
mentions teh MethodExpression but says nothing about the literal validatorId
that can be used too.