finished UBA NRT with the new database structure using the REST API (also added minor fixes to REST API and NRT changelog behaviour)

#17: REST APIs to changelog tables are build; #9: patch API for stationmeta creates a separate changelog entry for every field changed in the metadata

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

#3: now nested human readable download is established for timeseries; TBD: do this for all other modesl

#8: common base and test base is in place (but teardown of test_base has to be worked on for chained pytests)

#4: nested upload/download for roles (timeseries) working in production and pytest (uploading codes not human readable version)

#4: a typo made my days and nights long; after git crash do another upload; now detangling models_core and models_role again (different source code files)

#4: code completely messed up, but nested upload working; nevertheless download is NOT returning the nested view

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