New bullet types, projectile rewrite

* Refactors projectile Bump()
* Converts projectile_type var strings to paths
* Reorganizes bullet projectile paths
* Made a pass through all the bullet_act() definitions. Mainly ensured that damage_type is checked when dealing damage to certain objects. Removed stupid /turf bullet_act() override, replaced with on_hit() overrides on the relevant projectiles.

* Adds shotgun pellets projectile. Adds Raptor's shotgun slug sprite.
* Gives stunshots more of their own identity, refluffs them as taser cartridges for shotguns. They still aren't obtainable anywhere unless spawned.
* Makes projectiles pass through girders and cultgirders with a certain probability, unless the girder itself was clicked.
* Projectiles are also able to pass through grilles. Low damage projectiles have a chance to be blocked by grilles. High damage projectiles have a chance to have some damage absorbed by the grille.
* Makes projectiles for blanks invisible.
* Adds flash bullet types
* Adds support for 'penetrating' projectiles
* Swaps .45 and 9mm projectile types. .45s hit slightly harder, 9mils have more ammo capacity.

code/game/objects/structures/grille.dm

@@ -59,16 +59,33 @@
 			return !density
 
 /obj/structure/grille/bullet_act(var/obj/item/projectile/Proj)
-
 	if(!Proj)	return
 
 	//Tasers and the like should not damage grilles.
-	if(Proj.damage_type == HALLOSS)
+	if(!(Proj.damage_type == BRUTE || Proj.damage_type == BURN))
 		return
 
-	src.health -= Proj.damage*0.2
-	healthcheck()
-	return 0
+	//Flimsy grilles aren't so great at stopping projectiles. However they can absorb some of the impact
+	var/damage = Proj.damage
+	var/passthrough
+	if(damage > 30)
+		passthrough = 1
+		if(prob(20))
+			Proj.damage *= 0.5 //weaken the projectile
+	else
+		//weaker bullets are affected to a greater extent
+		if(prob(20))
+			passthrough = 0
+		else
+			Proj.damage *= 0.5 //weaken the projectile
+			passthrough = 1
+	
+	if(passthrough)
+		. = -1
+		damage *= 0.1 //if the bullet passes through then the grille avoids most of the damage
+	
+	src.health -= damage*0.2
+	spawn(0) healthcheck() //spawn to make sure we return properly if the grille is deleted
 
 /obj/structure/grille/attackby(obj/item/weapon/W as obj, mob/user as mob)
 	if(iswirecutter(W))