A code sample to differentiate the XU logging

If the logs of the two execution units (XUs) are redirected into the same file, they are difficult to differentiate.

The sample code of the RulesetChildRunner class demonstrates a way to easily identify the messages from two XUs (main or dependent). The PrefixedPrintWriter class extends PrintWriter to add an identifier at the beginning of each message.

See the code sample of the RulesetChildRunner class for adding the identifier of the XU:

xuCfg.setLogWriter(new PrefixedPrintWriter(System.out, "[XUCHILD] "));