Add linux userspace program; Move ndp out of icmpv6 (analoge to ARP); Remove getMTU from Sendbuffer API (use interface->getMTU); Move IPv4 ARP to ipv4/ethernet/ (analoge to ipv6/ethernet/ndp*); Add combined neighbour cache to ip/; Move find_route/resolveRoute for ipv6 packet routing from Router class to the IPv6 class (analoge to IPv4::resolveRoute)