IPv6 tunnel detection

Hello
I extended the plugin to detect and report if the traffic comes from an Teredo/6to4 address.
Feel free to reject or to propose changes, if something is wrong/missing.

The image below was generated by the "IP protocol evolution" widget:

![tunnel-detector](https://f.cloud.github.com/assets/4595369/797584/e31320ec-ed4d-11e2-89e2-ae3c7aa3ccc2.png)