Fs mount outside of root

The change in PathTranslator fixes an issue when using the mount and the root feature of the Trireme Sandbox at the same time. When mounts exist outside of the root set, reverse translation did not yield the correct result.

Furthermore, on Windows some APIs prefix pathnames using \\?\ UNC notation. This is not recognized by NIO's Files API. The simple fix is to strip this away.

Finally, in executeNetworkCallbacks() the removal of the selector key potentially comes to late, when the JavaScript code starts follow-up network operations.