Add support for new data sources

We are now providing the parquet and aggregated files out of the box. The change should be reflected in the package to download the parquets (if needed), to download the aggregates and to daily create these files.

Todo:

• Add support in the prepare step for the new, pre-processed parquet files.
• Add helper script to maintain and produce the new files daily.
• Add setup step in the docker image to download the aggregates on first startup.
• Update the documentation accordingly.