function merge(dst, src, ifNotSet) { // used by converters
    for (var keys = Object.keys(src), i = 0; i < keys.length; ++i)
        if (dst[keys[i]] === undefined || !ifNotSet)
            dst[keys[i]] = src[keys[i]];
    return dst;
}
Merges the properties of the source object into the destination object.
@memberof util
@param {Object.<string,*>} dst Destination object
@param {Object.<string,*>} src Source object
@param {boolean} [ifNotSet=false] Merges only if the key is not already set
@returns {Object.<string,*>} Destination object