Replace deprecated XMLHelper with new one

[ZakarFin]

Requires a test case

[jampukka]

This should just work, no?

[ZakarFin]

It should, but I haven't had the time to test it really :)

[ZakarFin]

I removed the try/catch since any uncaught exception is caught in https://github.com/oskariorg/oskari-server/blob/master/service-control/src/main/java/fi/nls/oskari/control/ActionControl.java#L146 and that throws the same ActionException as this one and includes the cause on it or in case of an ActionException throws it as is. So the try catch is only really changing the message that is logged and I don't think we care about that as much. These will be logged here https://github.com/oskariorg/oskari-server/blob/master/servlet-map/src/main/java/fi/nls/oskari/AjaxController.java#L44-L51