sortById = (a, b) => {
	if (a.id < b.id) return -1;
	if (b.id < a.id) return 1;
	return 0;
}
A convenience method used to sort chunks based on their id's
@param {ChunkGroup} a first sorting comparator
@param {ChunkGroup} b second sorting comparator
@returns {1|0|-1} a sorting index to determine order