Make geocoding faster

[teropa]

1. If "From" is the user's current location. We may already know the coordinates. Pass them as-is from the client.
2. The two geocoding requests can be done in parallel
3. A geocoding cache on the server might not be a bad idea. A cache of, say, 2000 hotspots (like "Rautatientori"), would likely eliminate a lot of requests. Could use ehcache or some other lib with a decent LFU implementation.