Feature Request: Unique thread names for PC instances for logging

Parallel consumer assigns names to its internal control threads which look like: `pc-broker-poll`, `pc-control`.

We have a scenario with multiple PC instances within one Java application. In that case we can't easily identify to which PC instance a log entry belongs (because even when logging the thread ids, it won't be directly visible which pc-control and pc-broker-poll threads belong together).

As improvement I'd suggest to internally generate an id for each PC instance that is created and put it into the thread names (like `pc-1-broker-poll`, `pc-1-control`, `pc-2-broker-poll`, `pc-2-control`, ...).