remove Spy game mode, add Team Deathmatch game mode

[SgtBriar]

I quite like Spy, and while it's not without its faults it's far better than TDM would be. Team Deathmatch WAS in the game, but removed because byond's combat engine sucks - at least with spy the opportunity for subtlety exists. Spy should not be removed and I'd be apprehensive at best about adding a TDM mode in.