Balance fixes for traitor game mode

1) Protected jobs fix. IAA can't become a traitor now
2) traitor_scaling_coeff is 1 traitor per 7 players. Less traitors in
game round now.
3) Two kill objectives for traitor-AI instead of one.
4) Brig objective is no more.
5) Hijack is possible now. One hijack per 120 traitors.
6) Traitors now have 1, 2 or 3 objectives.