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/mob/holder.dm

@@ -5,6 +5,8 @@ var/list/holder_mob_icon_cache = list()
 	name = "holder"
 	desc = "You shouldn't ever see this."
 	icon = 'icons/mob/npc/held_mobs.dmi'
+	randpixel = 0
+	center_of_mass = null
 	slot_flags = 0
 	sprite_sheets = list("Vox" = 'icons/mob/species/vox/head.dmi')
 	origin_tech = null

code/modules/mob/inventory.dm

@@ -164,7 +164,7 @@ var/list/slot_equipment_priority = list( \
 
 // Removes an item from inventory and places it in the target atom.
 // If canremove or other conditions need to be checked then use unEquip instead.
-/mob/proc/drop_from_inventory(var/obj/item/W, var/atom/target = null)
+/mob/proc/drop_from_inventory(var/obj/item/W, var/atom/target)
 	if(W)
 		if(!target)
 			target = loc
@@ -252,10 +252,10 @@ var/list/slot_equipment_priority = list( \
 	return slot
 
 //This differs from remove_from_mob() in that it checks if the item can be unequipped first.
-/mob/proc/unEquip(obj/item/I, force = 0) //Force overrides NODROP for things like wizarditis and admin undress.
+/mob/proc/unEquip(obj/item/I, force = 0, var/atom/target) //Force overrides NODROP for things like wizarditis and admin undress.
 	if(!(force || canUnEquip(I)))
 		return
-	drop_from_inventory(I)
+	drop_from_inventory(I, target)
 	return 1
 
 
@@ -375,6 +375,9 @@ var/list/slot_equipment_priority = list( \
 			step(src, inertia_dir)
 */
 
+		if(istype(item,/obj/item))
+			var/obj/item/W = item
+			W.randpixel_xy()
 
 		item.throw_at(target, item.throw_range, item.throw_speed, src)