Boss class reroll like zombie class reroll

[ghost]

Add support for boss-class rerolls when the gamemode's escape stage is ESCAPESTAGE_BOSS, would have to blacklist some boss classes like Shade since the bots don't know how to use them.

[Dadido3]

Will look into it once i have some free time

[ghost]

Infact just add support for bots being able to run zs_bossclass and then choose a value from a preset table of lists, this supports both the custom addition of bots being able to rise as bosses and said spawn as random bosses during ESCAPESTAGE_BOSS, seems somewhat easy. I will potentially look into this once I'm back from my trip to London.