#3,#4: nested uploads/downloads using controlled vocabulary; still to investigate: how to load enum_tables at beginning (this commit is a workaround)

almost done: using human readable controlled vocabulary for upload; TBD: using human readable controlled vocabulary for download, adapting pytests

#4: nested upload for stations done; TBD: more testing (esp. pytest), use controlled vocabulary (related to #3)

#4: defined association tables also in models; now using one base for the whole app 'toardb'; this has now also to be adapted to test_base

created ONE toardb app, also adapted pytests for toardb app (still very last test will throw an error for teardown; inserted example for url percent encoding