Map selection

[monban]

In the lobby, players should be able to vote on the map they want to play on.

This can initially be implemented as just a button that opens a pop-up and allows players to select or not select maps. When the server moves to the "main game" phase, a map will be selected based on the votes of all players.

The game design team will later give input as to how this can be made more interesting. (Maybe each player has their own "train ticket", on which they choose the destination, giving a more diegetic map selection experience?)