Misc tweaks (#3916)

changes:

/obj/visual_effect has been repathed to /obj/effect/visual.
Openspace movables will no longer use the space plane when on an openturf mimicing a space turf.
Lights now only update on direction change if your direction actually changed.
Fixed some bad set_dir() procs that were either pointless or that didn't return parent.
Mapped-in or maint dirtier-spawned glowing goo no longer self-deletes after 2 minutes.
Fixed an issue that may have caused some openspace movables to not properly handle direction changes.

code/game/objects/structures/stool_bed_chair_nest/chairs.dm

@@ -66,7 +66,7 @@
 		add_overlay(stool_cache[cache_key])
 
 /obj/structure/bed/chair/set_dir()
-	..()
+	. = ..()
 	if(buckled_mob)
 		buckled_mob.set_dir(dir)
 

code/game/objects/structures/stool_bed_chair_nest/wheelchair.dm

@@ -14,7 +14,7 @@
 	add_overlay(image(icon = 'icons/obj/furniture.dmi', icon_state = "w_overlay", layer = FLY_LAYER))
 
 /obj/structure/bed/chair/wheelchair/set_dir()
-	..()
+	. = ..()
 	if(buckled_mob)
 		buckled_mob.set_dir(dir)