Removed area.uid var and /area/New()

- var/uid was used in only a handful of places.  Because areas are singletons
  it is safe to replace the uid with \ref, areas don't get deleted.
- And with that /area/New() is empty, we can remove it!

code/ATMOSPHERICS/components/unary/vent_pump.dm

@@ -85,7 +85,7 @@
 
 	icon = null
 	initial_loc = get_area(loc)
-	area_uid = initial_loc.uid
+	area_uid = "\ref[initial_loc]"
 	if (!id_tag)
 		assign_uid()
 		id_tag = num2text(uid)

code/ATMOSPHERICS/components/unary/vent_scrubber.dm

@@ -38,7 +38,7 @@
 
 	icon = null
 	initial_loc = get_area(loc)
-	area_uid = initial_loc.uid
+	area_uid = "\ref[initial_loc]"
 	if (!id_tag)
 		assign_uid()
 		id_tag = num2text(uid)