Limit the anti-PvP logging death mechanism

[jwflory]

Whenever you log into the arena, you will automatically be killed, as a way to protect against PvP logging. However, this protection is enabled for the entire structure, as compared to just the actual arena.

This can cause issues if an administrator chooses to use the arena in a way that forces players to spawn in the lobby room of the arena, effectively killing them immediately upon logging in, even if they weren't PvP logging.

The best fix for this would be to find a way to set an "arena zone" in the config.yml (and can be set in-game, of course) by creating a cuboid region, checking if a player logs in the area of that region, and if true, kill the player.

This allows the administrator to set a custom-sized arena and be creative with how they choose to implement IceBall on the server.