Changes obj/effect/blob,spider,swarmer,energy_net,spacevines to be ob/structures instead, since you can hit and destroy them.

Adds a large ash and large molten item decal (for future use)
simplifies decal/cleanable/replace_decal() code a bit.
Changes construction() proc to on_construction() for consistency, same for deconstruction().
Made a deconstruct() proc for machinery and computer (also for future use).

code/modules/shuttle/supply.dm

@@ -1,8 +1,8 @@
 var/list/blacklisted_cargo_types = typecacheof(list(
 		/mob/living,
-		/obj/effect/blob,
+		/obj/structure/blob,
 		/obj/effect/rune,
-		/obj/effect/spider/spiderling,
+		/obj/structure/spider/spiderling,
 		/obj/item/weapon/disk/nuclear,
 		/obj/machinery/nuclearbomb,
 		/obj/item/device/radio/beacon,