Merge pull request #111 from rayburgemeestre/network_multiplayer

Network multiplayer
Merge pull request #112 from rayburgemeestre/network_multiplayer

Add forgotten CommandKeepAlive + CommandKeepAliveOk
Compiling on Windows now works again :)
Merge pull request #113 from rayburgemeestre/network_multiplayer

Fix problem that player deaths would accidentally trigger a state change...
Fix with switching from spectator to non-spectator. "Non-spectator" states are broadcasted properly