Host quitting rated games

[elexis]

Often players on the lobby quit the game in order to avoid getting a negative rating.

A simple and strict approach would be to reduce the rating if the server disappears, even if it was a power blackout or a crash.

A less strict approach would be to detect the shutdown. Both clicking on the exit button and closing the game with Alt+F4 (sending the exit signal) can be catched in the destructor of the CNetServerWorker() for example (maybe we can find a nicer place). The host quitting the server could send a packet to the lobby that he just quit a rated game. This means we abuse can also be tracked, allowing more accounts to be banned.