New data source for Switzerland - fix for #412

[RichardMN]

This is a WIP because the data cleaning hasn't been written yet, but check out the download function!

This addresses #412. As it is it has pushed the old Switzerland code into a new class (SwitzerlandAlt which has the amusing senses of both "old Switzerland" and "alternate Switzerland") and would replace them with the new Switzerland class.

The download function grabs a JSON file to determine which CSV files to download and uses both the download and the download_JSON methods from DataClass.

Cleaning code is to follow. There are other data streams available (including breaking out the data according to vaccination status) so I am open to votes on which to try to include and how.

[github-actions[bot]]

👋 Thanks for opening this pull request! Can you please run through the following checklist before requesting review (ticking as complete or if not relevant).

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