reorganise code

[katrinleinweber]

Currently, it's organised by topic, but that doesn't seem to be very elegant. Consider alternative organisations of the .R files, like by:

• data source current JSON & history
• code type (functions, processing steps, plotting, etc.)
• or even create a package

[katrinleinweber]

I never got around to doing this. I'm sorry.

[extua]

Closing this as part of issue cleanup