Added isValidLocation method, removed InvalidLocationException from throws list of getLocationForCoordinates(Vector2D) and deleted method getLocationForCoordinates(double x, double z)
Added isValidLocation method, removed InvalidLocationException from throws list of getLocationForCoordinates(Vector2D) and deleted method getLocationForCoordinates(double x, double z).  Removed most instances of thrown InvalidLocationException and replaced with a comparison.