Engine: * Modified gas grenade and added graphics to it (better get a nose clip!) * Added the ability to tint visual gears * Added the ability to tint explosion effects * Birdy's eggs now cause a small green explosion

Skip collision on X for barrels that aren't knocked over

Increase minimum threshold for barrel damage to reduce likelihood of blowing one up on jumping out, increase damage to compensate (may need tweaking). Only apply dX for collision w/ kick if barrel is rolling.