Previously I've asked about streaming a single file back to the client and got some good insight as to how to accomplish this with `transferFrom`, but this misses out on all the extra features like resuming transfers, cached content, etc. It would be very nice Undertow offered a static utility method to serve up File, Path, and URL providing all of this functionality that is currently contained in ResourceHandler (https://github.com/undertow-io/undertow/blob/master/core/src/main/java/io/undertow/server/handlers/resource/ResourceHandler.java#L155).

I don't think it would be difficult to extract all of that out of the private method and simply have ResourceHandler call the static method. Stuart, what do you think?

I'd even be willing to do the leg-work if you'd be willing to accept a PR for it.