fix erroring spec regarding permissions

In ontology_spec the IRI-Processing-Try-Again example failed with a
double-create of the same permission. This now only creates new
permission if there does not yet exist an applicable one.
remove double-structure loading in tests

db:migrate:clean also rebuilds the structure
of the database so we do not need load_structure/load_schema
during tests anymore.
add migration to correct version-data for children.
Merge branch 'staging' into 998-show_correct_version_list_for_children