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/arcade/arcade_base.dm

@@ -131,7 +131,7 @@
 			T.amount = "[token_price]"
 		T.source_terminal = src.name
 		T.date = current_date_string
-		T.time = worldtime2text()
+		T.time = station_time_timestamp()
 		customer_account.transaction_log.Add(T)
 		return 1