Migrate the validation checks to the schema

[skinkie]

Currently our validation checks are done within NeTEx_publication.xsd, this creates a big file, that eventually gets into a big mess, and from the perspective of the schema editor and reviewer does not know if the change is complete. In addition some restrictions cannot be applied from a single top file.

Proposal to change the restriction into the files with the specific structure.

This will obviously get into the situation where users of XML Spy need to do a feature request with their vendor to disable restriction checking, since everything will then be restricted. I can imagine a derived schema not having restrictions at all.

[skinkie]

Nice idea, it does not work :(