examine signature changed to include distance

- distance is INFINITE, 0, or a positive integer based on get_dist() between
the examiner and examinee's turfs when they are on the same Z. When the
examiner is dead or a ghost, distance is always 0.
- also updates /examine( implementations to use it!
- adds w_class_to_name proc for reusing "It is a X item." examine behavior.

code/modules/research/message_server.dm

@@ -423,4 +423,4 @@ var/global/obj/machinery/blackbox_recorder/blackbox
 
 	if(!FV) return
 
-	FV.add_details(details)
+	FV.add_details(details)