Add Map support

[QuImUfu]

I'd love to be able to use maps, e.g. Map<String, Enum> as config options.

[Motschen]

It is already possible to edit the json files for this kind of option, but I'm not sure how I could implement it in the UI and if it would really be used that much.
If you have any idea how to get this across visually, please lmk.
Also, I'd appreciate an example of a use case for String-Enum maps in the config.