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/NTNRC/conversation.dm

@@ -21,12 +21,12 @@ var/global/static/ntnrc_uid = 0
 	return ..()
 
 /datum/ntnet_conversation/proc/add_message(message, username)
-	message = "[worldtime2text()] [username]: [message]"
+	message = "[station_time_timestamp()] [username]: [message]"
 	messages.Add(message)
 	trim_message_list()
 
 /datum/ntnet_conversation/proc/add_status_message(message)
-	messages.Add("[worldtime2text()] -!- [message]")
+	messages.Add("[station_time_timestamp()] -!- [message]")
 	trim_message_list()
 
 /datum/ntnet_conversation/proc/trim_message_list()

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