Disconnects clients who have not joined the round before restarting

- In an effort to decrease the number of unneeded client connections, I've made it so when the round ends, all the clients who are in the lobby get kicked before the restart. This is only effective when rounds end 'organically' (not when restart commands or votes are used, for example). The intention is to prevent people from leaving their computers on and connected indefinitely, because all clients contribute to the total. The assumption is that if you are in the lobby when the round ends, you have not participated in the previous round, meaning you are probably not actually present.

- Also added a button to the player panel, which allows admins to do the same thing. The admin's name is reported to all the kicked clients.