Adds a reset button for the Thunderdome

You have the option of deleting mobs or leaving them alone.

Requested by @Hornygranny

code/modules/admin/admin.dm

@@ -433,6 +433,7 @@ var/global/floorIsLava = 0
 		dat += {"
 			<B>Fun Secrets</B><BR>
 			<BR>
+			<A href='?src=\ref[src];secretsfun=tdomereset'>Reset Thunderdome to default state</A><BR>
 			<A href='?src=\ref[src];secretsfun=virus'>Trigger a Virus Outbreak</A><BR>
 			<A href='?src=\ref[src];secretsfun=monkey'>Turn all humans into monkeys</A><BR>
 			<A href='?src=\ref[src];secretsfun=allspecies'>Change the species of all humans</A><BR>

code/modules/admin/topic.dm

@@ -1597,6 +1597,25 @@
 		var/datum/round_event/E
 		var/ok = 0
 		switch(href_list["secretsfun"])
+			if("tdomereset")
+				var/delete_mobs = alert("Clear all mobs?","Confirm","Yes","No","Cancel")
+				if(delete_mobs == "Cancel")
+					return
+
+				var/area/thunderdome = locate(/area/tdome/arena)
+				if(delete_mobs == "Yes")
+					for(var/mob/living/mob in thunderdome)
+						qdel(mob) //Clear mobs
+				for(var/obj/obj in thunderdome)
+					if(!istype(obj,/obj/machinery/camera))
+						qdel(obj) //Clear objects
+
+				var/area/template = locate(/area/tdome/arena_source)
+				template.copy_contents_to(thunderdome)
+
+				log_admin("[key_name(usr)] reset the thunderdome to default.", 1)
+				message_admins("<span class='adminnotice'>[key_name_admin(usr)] reset the thunderdome to default.</span>", 1)
+
 			if("monkey")
 				feedback_inc("admin_secrets_fun_used",1)
 				feedback_add_details("admin_secrets_fun_used","M")