Allows items to specify which icon files are used for specific slots, moves gun icons to a separate file

code/modules/projectiles/gun.dm

@@ -3,6 +3,10 @@
 	name = "gun"
 	desc = "Its a gun. It's pretty terrible, though."
 	icon = 'icons/obj/gun.dmi'
+	item_icons = list(
+		icon_l_hand = 'icons/mob/items/lefthand_guns.dmi',
+		icon_r_hand = 'icons/mob/items/righthand_guns.dmi',
+		)
 	icon_state = "detective"
 	item_state = "gun"
 	flags =  CONDUCT

code/modules/projectiles/guns/energy/special.dm

@@ -121,6 +121,7 @@
 	name = "staff of change"
 	desc = "An artefact that spits bolts of coruscating energy which cause the target's very form to reshape itself"
 	icon = 'icons/obj/gun.dmi'
+	item_icons = null
 	icon_state = "staffofchange"
 	item_state = "staffofchange"
 	fire_sound = 'sound/weapons/emitter.ogg'
@@ -174,6 +175,7 @@ obj/item/weapon/gun/energy/staff/focus
 	desc = "It's a cute rubber duck.  With an evil gleam in it's eye."
 	projectile_type = /obj/item/projectile/icarus/pointdefense
 	icon = 'icons/obj/watercloset.dmi'
+	item_icons = null
 	icon_state = "rubberducky"
 	item_state = "rubberducky"
 	charge_cost = 0