Ports table item autoalign from Bay (#6946)

Made it so items get their pixel x/y reset on pickup.
    Thrown items now also get their pixel placement slightly randomized.
    Tweaked the center of mass on a boatload of items to be more accurate to their sprite art.
    Replaced a bunch of randomized pixel placement code into a unifying proc; randpixel_xy() that uses an item's randpixel var.

code/modules/projectiles/ammunition.dm

@@ -3,6 +3,7 @@
 	desc = "A bullet casing."
 	icon = 'icons/obj/ammo.dmi'
 	icon_state = "s-casing"
+	randpixel = 10
 	flags = CONDUCT
 	slot_flags = SLOT_BELT | SLOT_EARS
 	throwforce = 1
@@ -20,8 +21,7 @@
 	. = ..()
 	if(ispath(projectile_type))
 		BB = new projectile_type(src)
-	pixel_x = rand(-10, 10)
-	pixel_y = rand(-10, 10)
+	randpixel_xy()
 
 //removes the projectile from the ammo casing
 /obj/item/ammo_casing/proc/expend()

code/modules/projectiles/gun.dm

@@ -658,6 +658,7 @@
 		return unwield()
 
 /obj/item/weapon/gun/pickup(mob/user)
+	..()
 	if(is_wieldable)
 		unwield()