Flamethrower Rework

Created by: Shadowmech88

Reworks the flamethrower to be more of a directed weapon and less of a death-by-ambient-heat weapon.

Each tile in the stream of flame now persists for one second. During its life, it will deal burn damage to any mobs on that tile every 2/10ths of a second, as well as setting them on fire if possible. The fire plume will spread out toward the end, with the spread varying based on the pressure with which it was fired. As seen in this WebM: http://puu.sh/nazKv/0caa813efd.webm in which the first flamethrower is firing at 1013kPa, the second is firing at rougly 500kPa, and the third at roughly 200kPa. Damage scales with the temperature of the theoretical reaction between either the gases in the tank or, if there is no oxygen in the tank, between the gases in the tank and whatever oxygen happens to be on the tile. Damage is also affected by firing pressure. A pure-plasma flamethrower will fire harmless plasma puffs in a vacuum or otherwise oxygen-deprived environment. A flamethrower with oxygen in the tank will be able to fire in both of these. I've also added a sound for the flamethrower. The flamethrower no longer imparts heat to the local atmosphere.

Miscellaneous additions: Guns now have vars to determine whether they can be fired by hulks, MoMMIs, diona nymphs, advanced tool users, et cetera. This allows greater customization for who exactly can fire a particular gun.

Simple mobs, such as spiders, can now take burn damage.