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/paperwork/photocopier.dm

@@ -321,7 +321,7 @@
 					toner = 0
 
 
-/obj/machinery/photocopier/blob_act(obj/effect/blob/B)
+/obj/machinery/photocopier/blob_act(obj/structure/blob/B)
 	if(prob(50))
 		qdel(src)
 	else