Wrap field.error in Messages

FieldElements has some special logic to wrap a field with a FormError that has a value with a message key through Messages:

https://github.com/playframework/playframework/blob/2.2.x/framework/src/play/src/main/scala/views/helper/Helpers.scala#L34

Because the fragments here are using raw Field, that functionality is not there, so it must be added to the fragements.