The newest changes involve decoupling the following two tasks:
1) Checking whether an application is complete
2) Replaying its event logs

These were both done in ReplayListenerBus, which adds complexity when we try to do them separately in HistoryServer. The new code migrates the logic in (1) to EventLoggingListener, which is more sensible since the log formats are defined by EventLoggingListener in the first place.