Overthink rule to later binding definition

[JakobVogelsang]

At the moment, a later binding type reference is one that has the internal address set. The attribute intAddre in element ExtRef is NOT null. In the same way, message binding, data binding are references that do not have this attribute.

We see not problems with this definition with documentation type SCD files. See for example ABB SSC600. The ICT here works with message binding subscription, but at the end it also adds the link to the internal function (add the intAddr attribute). When you want to read such a file all of a sudden, the message binding editor will not show any subscriptions.

It is not easy to find a solution that fits all here, but I feel the one we implemented right now can be improved.