Add placeId to Place

[felixguendling]

From Matrix

I'm not sure what the exact use case is, but bus stops belonging to train stations and different platforms of one bus stop can easily be more than 100m apart. I think we're usually using 250 meters or even more, of course then it gets more likely to also show unrelated stops.

This could be improved if we add place_idx_t from the geocoding to the Place in the API?
Then it's clear what MOTIS considers to be "the same stop". The heuristic MOTIS uses for this is probably not really good at the moment but then we can improve it. Because this problem will pop up in other places as well (e.g. what to show as "one stop" on the map once we have this feature).