Nightshifts & Randomized Station Time

This commit adds the Nightshift lighting mode from /tg/. From 19:00 to
07:00 in station time, the station will go into a reduced-lighting mode,
with dimmed lights across the station.

In conjunction with this, there is a new configuration option to start
the shift time at a random time other than 12:00, so that players are
more likely to experience a night shift (as opposed to having to have a
7 hour round).

code/modules/security_levels/keycard authentication.dm

@@ -159,7 +159,7 @@
 				to_chat(usr, "<span class='warning'>All Emergency Response Teams are dispatched and can not be called at this time.</span>")
 				return
 			to_chat(usr, "<span class = 'notice'>ERT request transmitted.</span>")
-			print_centcom_report(ert_reason, worldtime2text() +" ERT Request")
+			print_centcom_report(ert_reason, station_time_timestamp() + " ERT Request")
 
 			var/fullmin_count = 0
 			for(var/client/C in admins)

code/modules/security_levels/security levels.dm

@@ -123,6 +123,7 @@
 			atc.reroute_traffic(yes = TRUE) // Tell them fuck off we're busy.
 		else
 			atc.reroute_traffic(yes = FALSE)
+		SSnightshift.check_nightshift()
 
 	else
 		return