Qserv: Build TCP socket networking servers

This class can be used as a based to create TCP socked based networking servers.

It can handle connection requests and calls event handling functions that maybe overridden by subclasses to implement server application specific behavior.

The class provides the event handling functions: onincomming, onaccept, onclose, onstart, onshutdown and onstartlisten.

Alternatively, it can also call application defined callback functions to handle server events.