[OSM] Cash the responses

[OhmSpectator]

Overpass API requests take a long time to be handled, but the responses are not changed that often. Try to cache them.

[OhmSpectator]

https://github.com/requests-cache/requests-cache

[OhmSpectator]

The most problematic request, the Overpass API is done now via overpy package. So we cannot control the caches with the requests_cache package there. Check the package itself or try to fix it and propose a solution with caching to the overpy master.

[OhmSpectator]

https://python-overpy.readthedocs.io/en/latest/

[OhmSpectator]

Another option would be just to serialize the responses per query string.