Additionally, delete DedicatedPlayers who disconnect.
Previously, all disconnected DedicatedPlayers were still kept in memory, but never used again. There was code that suggested they were meant to be reused upon reconnecting, but that reuse had never actually been implemented, and would probably not be that useful anyway.
Additionally, print player guids using their string representations for consistency.
The creation and updating of DedicatedPlayer references remains very inelegant, but this commit is the first step towards fixing that.
