Loopback working example.

This release is mainy for those looking to test loopback.
It configures W5300 on TOE board with IP 192.168.0.7 and MAC 00:08:DC:01:02:03
You can send UDP packets and receive correctly with this release.
Refer to the python scripts for some example of testing it.
The speed takes into account the payload only data. It will be slightly higher.
Speed (TX+RX) bits. 19.9Mbps