Added ability to disable bosses using logic_classunlock

-Added Key "bossesenabled"
-added input "setbossesenabled"
-Updated FGD with above changed
-Cleaned up FGD
Changed function call from KeyValue to SetKeyValue
fixed being able to pickup pistol ammo anytime

Gave fists an ammo type so that the check made GAMEMODE.weaponrequiredforammo can function as intended.
Revert to 66fead7
Merge pull request #16 from BClark09/master

Added ability to disable bosses using logic_classunlock
Merge pull request #15 from BClark09/patch-1

fixed being able to pickup pistol ammo anytime
Merge branch 'master' of https://github.com/JetBoom/zombiesurvival