Quick Play: Add leave bans

[smoogipoo]

In order to combat players leaving quick play rooms before they end, we should ban them from being able to queue again for a short while (10 minutes). Unlike the current 1 minute ban for declining a queue invitation, this one will require appropriate messaging.

Database:

matchmaking_user_bans (int user_id, timestamp end_time, enum reason);

Server:

enum MatchmakingBanReason
{
    DeclinedQueue,
    EarlyLeave
}