Create support for knx-IP discovery to support direct ip programming

[thelsing]

[nanosonde]

Hi!

I am currently working on this indirectly, as I have implemented a simple cEMI Server with KNX USB data interface support. ETS and Net'n'Node recognize it already. While implementing this, I am keeping this in mind. Once this is done, it should be rather easy to add support for this too. However, so far I have NOT implemented cEMI Translayer Mode as I hope that the normal data link layer is enough (see PID_COMM_MODE).

BTW: I have already experimented with IP discovery. Answering just the SEARCH_REQ with a proper response (only routing, no tunneling) is enough to make a generic multicast ethernet interface apear in ETS (just like a normal router) that you can select to program a device (0x57B0) via IP and data link layer (instead of cEMI transport layer).