NeTEx Remove all order attributes which are informative

In #560 we have identified that the StopPointInJourneyPatternRef in virtually all examples ends up incomplete and is therefore hidden in validation because the referee does not provide all required field. From XML Schema perspective, the explicit order is optional, since the sequence already requires ordered processing. I do not dispute that it is nice to have a numeric value specifying order, but since the id+version element on its own must be unique anyway I would say that removing the order element all together for sequences makes a lot more sense. Obviously, this is XML specific. Any other implementation should take into account that the sequence is in fact an OrderedList and not just a List.