Connection persistence and container ID tracking in Redis

[karashiiro]

If the lobby server goes down for some reason, connections should not be dropped when the server is restarted. The game instances behind the lobby server will still be running, so no game state will be lost. All that needs to be done to restore connections is to persist the connection map into a database of some kind.

[karashiiro]

While we're at it, we should persist the connection IDs so we can stop closed containers with no players.

[karashiiro]

While we could leave empty containers running to reduce startup times, that would also prevent us from reloading addons without restarting the entire setup.

[karashiiro]

Redis should be configured with RDB+AOF because we don't want any data loss to happen at all. Connections can be opened and closed within a few minutes, and we don't want recent joiners to not have their connections restored.

[karashiiro]

One half of this is done 29054ea, now the actual connections need to be persisted.

[karashiiro]

9e20406

The container connection is now persisted, so that complete rejoining can occur; in-game reconnection is next.

[karashiiro]

32582be closing.