Humans on Fire system (DO NOT MERGE)

Bringing this out onto git for code review, yelling about how good/terrible this idea is, learning about datums and lag. Help me out here guys. Do NOT merge this.

New vars for mob/living
on_fire = 0 (Are we on fire?)
fire_stacks = 0 (Stacks of "fire", when this hits a certain amount decided in handle_fire(), you ignite)

New proc in mob/living/carbon/human/Life()
handle_fire() (Deals with being on fire)

New procs for mob/living
IgniteMob()
ExtinguishMob()

mob/living/carbon/human/fire_act() no longer simply bumps up body temperature, but instead adds to the fire_stacks var

This system is currently in no way finalized and would need heavy balancing before being implemented.