config changes for new adex structure with frequencies

The archives and datasets are now 'hardcoded' so, for example, lotss-dr2 is added to the datasets, it has to be added manually. This is not optimal but the frequencies are now mandatory in ADEX and they are not available in the database (yet).

This structure makes the filtering a lot easier on the ADEX side and only one API call to retrieve the config is needed (instead of 3 before).