Cities

**Please merge only after `dstc_tracking` has been merged.** Also, compare to `dstc_tracking`, not `master`.

Extension for more cities (including inferring the city based on stop and vice versa -- defaulting to main train/bus station). Added stations in Brno.

Only asks for a city if both stops exist in more cities, e.g. "Zoologická zahrada" and "Přístaviště" in Prague and Brno.

Known issues:
- SLU can't handle stops that are named the same as cities (Chodov, Tábor are therefore omitted from the list of cities -- and Tábor is quite large to be ignored)
- SLU can't handle stops that only differ in casing ("Bílá Hora" in Prague and "Bílá hora" in Brno... "bílá hora" is always recognized as the first one of them).