Casing rotation

Spent casings ejected from firearms will spin as they 'tumble' towards the ground.
Improved sprites for shotgun shells
Improved sprite for bullet projectile.

Conflicts:
	code/__HELPERS/matrices.dm
	code/modules/projectiles/guns/projectile.dm
	icons/obj/ammo.dmi
	icons/obj/projectiles.dmi
Update shotgun.dm

shells spin faster
Conflicts:
	code/modules/projectiles/guns/projectile/shotgun.dm