persist datasets, minor cleanups

[jstriebel]

The dataset configs are stored in a json file and reapplied on startup.

Besides that I added smaller changes:

• Replace run script with docker-compose
• Cleanup Readme
• use sanic_cors to handle OPTIONS requests

[jstriebel]

The build currently failes because of a bug in mypy, which I already fixed (https://github.com/python/mypy/pull/6174). A new release including the fix is scheduled for tomorrow (https://github.com/python/mypy/issues/6130). You can verify the typing locally removing .mypy_cache manually (which I already did).

[jstriebel]

fixes #14