The whole OSM reading stuff should be in a separate source module 'import-osm' which needs a bit refactoring so that we can finally do

hopper = new GraphHopperOSM().setOSMFile(...)
hopper.importOrLoad()

and on Android etc we should be able to avoid setting OSM related stuff and just do:

hopper = new GraphHopper();
hopper.load(ghFolder)

We should use the change to separate OSM better from the core. Furthermore we could easier integrate other readers like #277 and #616.