Destroy() cleanups in VOREStation code

* Remove remaining hard del()'s in our code.
* Replace deleted() and gcDestroyed with QDELETED macro.
* Fix some strange calls directly to Del() (capital D)
* Make Destroy() return qdel hints.
* Make a few of the Destroy()'s more comprehensive in cleaning up references.
* In edited Destroy() procs, converted to use qdel_null and qdel_null_list macros when possible for pretty code.
* Removed unused variable `sleevecard`

code/modules/multiz/open_space_controller.dm

@@ -36,7 +36,7 @@
 
 	for(last_object in turfs_to_process_old)
 		var/turf/T = last_object
-		if(T && !T.gcDestroyed)
+		if(!QDELETED(T))
 			update_turf(T)
 		SCHECK