Moved zclass packaging to non-generated files.

Problem: Packaging of zclass generation scripts and example file was lost when generating.
Solution: Moved scripts to model/Makefile.am.supplement and example to project.xml as extra.
Question: Is this the correct way to package these things?
This is what I'm unsure of. I would like the example to be packaged with a dist, but it should have no effect on dependencies in the project. An alternative could be to edit the automake gsl script to output a EXTRA_DIST += into src/Makefile.am.supplement. Perhaps also amend project.xml with a new tag to specify such files in general?