private static float getCacheScalingFactor(final boolean applyScaling) {
        return applyScaling ? scalingFactorCacheIcons : 1;
    }
Create a LayerDrawable showing the caches difficulty and terrain rating. If the connector doesn't support D/T show a "-" instead, if the info is missing (not loaded) a "?"
@param res           Resources bundle
@param difficulty    Difficulty rating
@param terrain       Terrain rating
@return              LayerDrawable composed of round background and foreground showing the ratings
main/src/main/java/cgeo/geocaching/utils/MapMarkerUtils.java