remove the sub-area system

Removes area/list/related and area/master.
They were only used by the old lighting subarea system.

Signed-off-by: Mloc <colmohici@gmail.com>

code/modules/power/gravitygenerator.dm

@@ -50,8 +50,8 @@
 	for(var/area/A in range(src,effectiverange))
 		if(A.name == "Space")
 			continue // No (de)gravitizing space.
-		if(A.master && !( A.master in localareas) )
-			localareas += A.master
+		if(!(A in localareas))
+			localareas += A
 
 /obj/machinery/computer/gravity_control_computer/proc/findgenerator()
 	var/obj/machinery/gravity_generator/foundgenerator = null
@@ -125,7 +125,7 @@
 			for(var/area/A in gravity_generator:localareas)
 				var/obj/machinery/gravity_generator/G
 				for(G in machines)
-					if((A.master in G.localareas) && (G.on))
+					if((A in G.localareas) && (G.on))
 						break
 				if(!G)
 					A.gravitychange(0,A)
@@ -137,4 +137,4 @@
 				A.gravitychange(1,A)
 
 		src.updateUsrDialog()
-		return
+		return