Automate server restart

[a-nikolaev]

Make the following thing:

When:

• All clients leave, or
• There is a winner, or
• all clients are defeated

the server continues running for extra 5-15 seconds, and then restarts the game.

This automated restart can be the default behavior, or turned on with a command line argument (say, -L for loop, or something like this). It is good to have this option for single player too. The format can be -L seconds-to-wait.

[Sicness]

After that we can think about running public dedicated servers :)