Integration of TCP message server for inter-process communication (e.g. with KNIME) #899 

Message server / request handler / command processor able to:
- Listen to TCP messages at a given port
- Handle received commands: Currently only "setViewerPos" (change volumina viewer position) and "handshake" (establish connection to client), but more commands can easily be implemented
- Connect to clients and send messages to them from within every applet (e.g. to highlight/unhighlight specific objects in KNIME from the Object Classification applet)
- Export objects to KNIME (only in debug-mode)