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/nifsoft/nif.dm

@@ -100,16 +100,11 @@ You can also set the stat of a NIF to NIF_TEMPFAIL without any issues to disable
 	if(human)
 		human.nif = null
 		human = null
-	for(var/S in nifsofts)
-		if(S)
-			qdel(S)
-	if(nif_hud)
-		qdel(nif_hud)
-	if(comm)
-		qdel(comm)
-
-	nifsofts.Cut()
-	..()
+	qdel_null_list(nifsofts)
+	qdel_null(nif_hud)
+	qdel_null(comm)
+	nifsofts_life.Cut()
+	return ..()
 
 //Being implanted in some mob
 /obj/item/device/nif/proc/implant(var/mob/living/carbon/human/H)
@@ -541,7 +536,7 @@ You can also set the stat of a NIF to NIF_TEMPFAIL without any issues to disable
 	if(nif)
 		nif.nif_hud = null
 		nif = null
-	..()
+	return ..()
 
 /obj/item/clothing/glasses/hud/nif_hud/process_hud(M,var/thing)
 	//Faster checking with local var, and this is called often so I want fast.

code/modules/nifsoft/nif_statpanel.dm

@@ -47,7 +47,7 @@
 
 /obj/effect/nif_stat/Destroy()
 	nifsoft = null
-	..()
+	return ..()
 
 /obj/effect/nif_stat/proc/atom_button_text()
 	name = nifsoft.stat_text()

code/modules/nifsoft/nifsoft.dm

@@ -50,11 +50,10 @@
 //Destructor cleans up the software and nif reference
 /datum/nifsoft/Destroy()
 	if(nif)
-		uninstall(nif)
+		uninstall()
 		nif = null
-	qdel(stat_line)
-	stat_line = null
-	..()
+	qdel_null(stat_line)
+	return ..()
 
 //Called when the software is installed in the NIF
 /datum/nifsoft/proc/install()
@@ -67,7 +66,8 @@
 	if(nif)
 		. = nif.uninstall(src)
 		nif = null
-	qdel(src)
+	if(!QDESTROYING(src))
+		qdel(src)
 
 //Called every life() tick on a mob on active implants
 /datum/nifsoft/proc/life(var/mob/living/carbon/human/human)
@@ -126,7 +126,7 @@
 /datum/nifsoft/package/Destroy()
 	software.Cut()
 	software = null
-	..()
+	return ..()
 
 /////////////////
 // A NIFSoft Disk

code/modules/nifsoft/software/05_health.dm

@@ -12,8 +12,8 @@
 		arscreen = new(nif)
 
 	Destroy()
-		qdel(arscreen)
-		..()
+		qdel_null(arscreen)
+		return ..()
 
 	activate()
 		if((. = ..()))

code/modules/nifsoft/software/13_soulcatcher.dm

@@ -25,11 +25,8 @@
 		load_settings()
 
 	Destroy()
-		for(var/brain in brainmobs)
-			var/mob/living/carbon/brain/caught_soul/CS = brain
-			qdel(CS)
-		brainmobs.Cut()
-		..()
+		qdel_null_list(brainmobs)
+		return ..()
 
 	install()
 		if((. = ..()))
@@ -249,10 +246,8 @@
 		soulcatcher = null
 	if(nif)
 		nif = null
-	if(mind && ckey)
-		src.ghostize()
 	container = null
-	..()
+	return ..()
 
 /mob/living/carbon/brain/caught_soul/Life()
 	if(!mind)

code/modules/nifsoft/software/14_commlink.dm

@@ -43,13 +43,14 @@
 		nif = newloc
 		nifsoft = soft
 		register_device(nif.human)
-		qdel(camera) //Not supported on internal one.
+		qdel_null(camera) //Not supported on internal one.
 
 	Destroy()
 		if(nif)
 			nif.comm = null
 			nif = null
-		..()
+		nifsoft = null
+		return ..()
 
 //So that only the owner's chat is relayed to others.
 /obj/item/device/communicator/commlink/hear_talk(mob/living/M, text, verb, datum/language/speaking)