public static Observable<BitmapDrawable> fetchDrawable(final String directionCode) {
        return HTML_IMAGE.fetchDrawable("https://www.geocaching.com/images/icons/compass/" + directionCode + ".gif");
    }
Retrieve the direction image corresponding to the direction code.

@param directionCode one of the eight cardinal points
@return an observable containing zero or more drawables (the last one being the freshest image)
main/src/main/java/cgeo/geocaching/ui/DirectionImage.java