Make falling in fire dangerous

Two changes, one is if you're unable to stand and in a fire, it hits all body parts, this is crazy dangerous and will kill most anything in a few turns. Fixes #8400 
The other is I toned down the rate at which fire damage inflicts the "onfire" effect.
Previously taking 1, 2, 3, 4, and 5 damage would have a 1%, 20%, 34%, 43% and 50% chance of lighting you on fire, and it just kept increasing after that.
Now it's a flat 1% chance of catching on fire per point of damage from fire.  This still adds up pretty quickly, but it's not the case anymore that every time you step into a fire (even a small fire) you catch on fire immediately.