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/modular_computers/computers/modular_computer/variables.dm

@@ -27,6 +27,8 @@
 
 	icon = null												// This thing isn't meant to be used on it's own. Subtypes should supply their own icon.
 	icon_state = null										// And no random pixelshifting on-creation either.
+	randpixel = 0
+	center_of_mass = null
 	var/icon_state_unpowered = null							// Icon state when the computer is turned off
 	var/icon_state_menu = "menu"							// Icon state overlay when the computer is turned on, but no program is loaded that would override the screen.
 	var/icon_state_screensaver = null