sub schema (SchemaAttributePathInstance) domain model extension + test re-factoring

* incl. new init_internal_schema.sql script (+ generation via code)
having had some trouble to find out about the differences of tearDown2 (seems not to exist anymore in recent branches), tearDown3 and tearDown, I suggest to use a more descriptiveName for tearDown3 like tearDownAfterMethod or at least rename to tearDown2