Multiplayer: Game testing and debugging

[smerkli]

The LAN multiplayer mode of Orxonox is still in early stages and not very well-tested. The only way to get this game mode to be more robust is to test it to uncover bugs and then fix them. This requires at least to people to play, temporary addition of more players from other projects might be a good idea as well.

Tests to be done include all game modes playable in multiplayer, chat, joining/leaving games, online/cross-platform multiplayer games.