ServerStuff - Todo till Alpha

[Earless]

I want to implement the following Server stuff before finishing the ALPHA game:

• Clients can not connect to a server midgame (so if a game is started, no further connections are allowed). This makes sure that everything works smoothly for everyone already playing.
• Duplicate ports will not be allowed. You can't start a server on a port which is already used.
• If the server (before starting the game) disconnects the server, everyone connected should be able to join another server without problems.
• If a client (before starting the game) disconnects from the server, the lobby should still be working as well as the game.
• (If time left:) When the server quits the game, everyone should be thrown out of the server.

[Earless]

As of now:

• You can't connect to a server which already started the game
• When initializing a server, a portnumber between 0 and 30000 will be chosen. So a negligible chance of starting a server on an already occupied port
• Server can disconnect the server (not in game); everyone gets kicked out of the lobby. They can start their own server without trouble after.
• Client can disconnect from the server (while in lobby); lobby is still working after, and the client can just continue doing whatever he likes.
• A client can discconect from the server (while ingame); the game continues on, without the left client (player gets destroyed). Moreover, the shown scores are still correct.

[Earless]

Now a server can also leave the game. If that happens, everyone get send back to the Main Menu.