#98 Add attacker side of the Memcrashed attack

This attack simulates the attacker-side of a Memcached amplification attack (publicly known as "Memcrashed"). As discussed in the meeting, gateways typically only see one side of the attack (attacker -> server or server -> victim), which is why we split the implementation of Memcrashed into two attacks. This attack only implements the first part, the victim-side will follow shortly. To specify the IP address of the victim, which is spoofed by the attacker, we introduced an additional parameter (ip.dst is occupied by the Memcached server).