changed ResourceHandlerRegistry.matchURL to return TryNbl rather than Nullable; thus failures may now be returned
changed resourceHandler in ResourceHandlerRegistery to a TryNbl; and added coded to lock the results
cleaned up ResourceHandlerRegistery.depthFirstRecursiveScanForFirstUrlMatch; it that much easier to understand now
added a cache for RegistryTree.children.reverse as a temporary step before removing entirely
removed the reverse nodes cache by using a more appropriate data structure