The DemoNetDriver is resilient to missing metadata files, and will still attempt to play the stream.
Each demo is now stored in its own directory with its metadata file.
NullNetworkReplayStreaming now handles generating the full path to the demo files, instead of the demorec and demoplay command handlers.
Updated ShooterGame to work with new directory structure.
#codereview john.pollard
[CL 2435846 by Ryan Gerleve in Main branch]