Include example VNFs into this repository

[mpeuster]

Right now they are here: https://github.com/mpeuster/vnf-bench-model/tree/dev/docker-vnfs

Attention: We cannot simply copy them because of licensing conflict.
Solution might be to use Suricata from official sources: E.g. the official ppa https://suricata-ids.org/download/

We need to add to out wiki documentation how those VNFs can be built and used.