Allow query by OSMID instead of Nominatim name

[mszell]

Useful sometimes to find specific places that are annoying. In my example some Italian cities gave their urban areas first instead of the municipality boundaries.

Request from Clement Sebastiao @csebastiao

[mszell]

Would be partially fixed by #206 and BikeNetKit/dataexport#15

[mszell]

We should probably change the city_name parameter anyway to city_query (because it's really a query, which just often coincides with the name), then we could make both acceptable, to be checked and decided to use as query string or osmid. (format for an ID: OSM type+id (N123, n123, W123, w123, R123, r123))