Scripts for inserting QC test candidates into the new database (bugs found and fixed), added csv API for downloading data

#9, #14: API for patching data (measurements) have been installed; data is not overwritten, but saved to table data_archive, a changelog entry is created

#11: still struggling with creating pdf (but now a little bit better) -- see (pandoc) command in issue

#3: added unique constraint to controlled vocabularies; added foreign keys (controlled vocabularies) to models

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

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

#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

#1: added another test (timeseries not existing); tried to have more user-friendly error messages; still struggling why I get doubled quotation marks now

#1: pytest for uploading data with no_autoflush now working; added timeshift_from_utc to data insertion; added error message if trying to insert duplicates

#1: pytest for data established; renamed date_time to datetime; needed 'no_autoflush' in timeseries queries

adapted sphinx documentation to new structure (ONE app); some pretty printing (fastAPI does not provide sphinx extensions like django)

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