Non-authoritative multiplayer

[Inspirateur]

In a non-authoritative multiplayer setting, the server just relays player's packets to each other, not checking if the players are sending valid stuff or cheating.
This is enough to play with friends but obviously isn't enough to support public servers. Nonetheless, it is the most sensible first step to take on the way to true multiplayer, as it is significantly easier to implement.

There should be a new Client/Server state enum controlling which systems run.

The server should:

• relay player positions/display players
• relay block changes
• send chunk data as they are loaded