Improve POI search

[karussell]

When we search for a railway station we have the problem in German that often the most important station is Hauptbahnhof but the match to "Bahnhof" is much worse although it should be much better.

Also there is a problem for different languages like " railway station" ... so we should think to index common POI names additionally to a POI for the different languages (airport, railway, post office, ...)