Experiment with Java Microbenchmark Harness (JMH)

[hopskipnfall]

Candidates for benchmarking:

• GameDataCache performance.
• Ping flow (receive ConnectMessage_PING, respond ConnectMessage_PONG)
• Handling a GameData packet
• Handling a CachedGameData packet

GameDataCache would be the easiest to start with because it only involves integrating with JMH. It could be interesting to experiment with hashing to improve contains() performance. We can also use recorded game inputs (which I have already).

[hopskipnfall]

It may be difficult to fix #219 until we have this.