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/modular_computers/NTNet/NTNet.dm

@@ -36,7 +36,7 @@ var/global/datum/ntnet/ntnet_global = new()
 
 // Simplified logging: Adds a log. log_string is mandatory parameter, source is optional.
 /datum/ntnet/proc/add_log(log_string, obj/item/weapon/computer_hardware/network_card/source = null)
-	var/log_text = "[worldtime2text()] - "
+	var/log_text = "[station_time_timestamp()] - "
 	if(source)
 		log_text += "[source.get_network_tag()] - "
 	else