Incendiary shotgun shells

Adds incendiary shotgun shells that do 20 brute damage and set the target on fire contained within a new subclass for incendiary bullets which also contains the bullets for the Dark Gygax's carbine. They can be made at hacked autolathes for the same metal cost as slugs and chemical dart shells. The shells are colour coded orange and the chemical dart shells also now have their own purple sprites.