Implement LogPacket command (previously unimplemented PacketLog) for TestClient.

As per the unimplemented command, this takes n number of packets and logs them to the given file.
This is done asynchronously and the user notified when packet logging is complete.
Add timestamp for each packet in logpacket command to correlate output with other logs
Implement some fairly harsh locking to stop multiple logging calls to logpacket TestClient command from stepping on each other.
Merge pull request #10 from justincc/master

Implement logpacket (previously unimplemented packetlog) command