Switch from Nominatim-only to Overpass+Nominatim search

[saerdnaer]

Nominatim now has a new api call which allows to get up to 50 addresses in one request. So we can finally can switch back to the Overpass Query, get the OSM object ids and request their addresses via XML or JSON

This would also allow to finally create a FinderApp instance for emergency=defibrillator

See also the new section in the Nominatim documentation: http://wiki.openstreetmap.org/wiki/Nominatim#Address_lookup