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/game/objects/items/weapons/material/ashtray.dm

@@ -2,6 +2,7 @@
 	name = "ashtray"
 	icon = 'icons/obj/ashtray.dmi'
 	icon_state = "blank"
+	randpixel = 5
 	force_divisor = 0.1
 	thrown_force_divisor = 0.1
 	var/image/base_image
@@ -13,8 +14,7 @@
 		qdel(src)
 		return
 	max_butts = round(material.hardness/10) //This is arbitrary but whatever.
-	src.pixel_y = rand(-5, 5)
-	src.pixel_x = rand(-6, 6)
+	randpixel_xy()
 	update_icon()
 	return
 

code/game/objects/items/weapons/material/shards.dm

@@ -5,6 +5,7 @@
 	icon = 'icons/obj/shards.dmi'
 	desc = "Made of nothing. How does this even exist?" // set based on material, if this desc is visible it's a bug (shards default to being made of glass)
 	icon_state = "large"
+	randpixel = 8
 	sharp = 1
 	edge = 1
 	w_class = 2
@@ -22,8 +23,7 @@
 		return
 
 	icon_state = "[material.shard_icon][pick("large", "medium", "small")]"
-	pixel_x = rand(-8, 8)
-	pixel_y = rand(-8, 8)
+	randpixel_xy()
 	update_icon()
 
 	if(material.shard_type)

code/game/objects/items/weapons/material/twohanded.dm

@@ -85,6 +85,7 @@
 	item_state = icon_state
 
 /obj/item/weapon/material/twohanded/pickup(mob/user)
+	..()
 	unwield()
 
 /obj/item/weapon/material/twohanded/attack_self(mob/user as mob)