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/research/stockparts.dm

@@ -3,14 +3,14 @@
 	desc = "What?"
 	gender = PLURAL
 	icon = 'icons/obj/stock_parts.dmi'
+	randpixel = 5
 	w_class = 2.0
 	var/rating = 1
 	drop_sound = 'sound/items/drop/glass.ogg'
 
 /obj/item/weapon/stock_parts/Initialize()
 	. = ..()
-	src.pixel_x = rand(-5.0, 5)
-	src.pixel_y = rand(-5.0, 5)
+	randpixel_xy()
 
 //Rank 1
 

code/modules/research/xenoarchaeology/geosample.dm

@@ -19,6 +19,7 @@
 	desc = "It looks extremely delicate."
 	icon = 'icons/obj/xenoarchaeology.dmi'
 	icon_state = "sliver1"	//0-4
+	randpixel = 8
 	w_class = 1
 	sharp = 1
 	//item_state = "electronic"
@@ -27,8 +28,7 @@
 
 /obj/item/weapon/rocksliver/New()
 	icon_state = "sliver[rand(1,3)]"
-	pixel_x = rand(0,16)-8
-	pixel_y = rand(0,8)-8
+	randpixel_xy()
 	create_reagents(50)
 	reagents.add_reagent("ground_rock",50)