Improve banning/kicking options

[gunchleoc]

1. For /warn, the server should prefix the username to the warning. The warned user might overlook it too easily otherwise. We could also add some player color on the client side.

2. I created a new game without starting it, kicked it, then started the game. The game could not be kicked again. So, any naughty game names will still appear in the list.

3. When a host is kicked from the lobby, they can still start and play their game

4. It would also be good if we could provide a kick/ban reason to the player.

5. We should display the duration of the ban to the user