[Nml-wg] New schema

[Freek Dijkstra]

I've just updated the schema to include PortGroups and LinkGroups and
list all relations that Jeroen recently send out to the list.

https://forge.ogf.org/sf/go/doc15481

Note that per UML standards, all abstract classes are now in italics.
The source document can be found in the Subversion repository. I also
added a schema that detailed the Relations as opposed to the class
hierarchy.

https://forge.ogf.org/svn/repos/nml-base/sources/NML-schema.graffle
https://forge.ogf.org/svn/repos/nml-base/NML-schema.pdf
https://forge.ogf.org/svn/repos/nml-base/NML-relations.pdf

Feedback is most appreciated (did I forget something, are there any
errors or omissions?)

Regards,
Freek