Change holidays into datums

Holidays are now actual datums with procs and vars and everything.
Holidays run a proc called celebrate() when it's time to celebrate them.
Currently none of them do anything but that should change, wink wink.
Holidays can now run for more than a day. The important ones, april fools,
christmas, halloween, new years, and easter, all last at least a week.
The idea is so people can celebrate christmas in game without having to,
you know, actually play on fucking christmas. And also to put a time limit
on how long stuff like the annoying spookoween closet skeletons will stick
around so it doesn't overstay its welcome and become annoying as shit like
last year.

The event SS now allows more than 1 holiday to run at a time.
This matters for new years + christmas, easter + april fools, easter + 4/20,
and any holiday that can happen on friday the 13th.
The events get stored in a list that's only initialized if there's an active
holiday so testing for potential holidays is still pretty easy.
Added more easter dates so we won't have to add more until 2040.
The current batch run out in 2017.

:-------------PARACODE NOTES------------:
Tied to event process
Extra procs for holidays to be able to run special events alone
Admin manual-override functionality maintained and ported to new system

code/controllers/Processes/event.dm

@@ -1,6 +1,48 @@
 /datum/controller/process/event/setup()
 	name = "event"
 	schedule_interval = 20 // every 2 seconds
+	if(!holiday_master)
+		holiday_master = new
+		holiday_master.Setup()
 
 /datum/controller/process/event/doWork()
-	event_manager.process()
+	event_manager.process()
+	holiday_master.process()
+
+/////////
+//Holiday controller
+/////////
+
+var/global/datum/controller/holiday/holiday_master //This has to be defined before world.
+
+/datum/controller/holiday
+	var/list/holidays
+
+/datum/controller/holiday/proc/Setup()
+	getHoliday()
+
+/datum/controller/holiday/proc/process()
+	if(holiday_master.holidays)
+		for(var/datum/holiday/H in holiday_master.holidays)
+			if(H.eventChance)
+				if(prob(H.eventChance))
+					H.handle_event()
+
+/datum/controller/holiday/proc/getHoliday()
+	if(!config.allow_holidays)	return //Holiday stuff was not enabled in the config!
+
+	var/YY = text2num(time2text(world.timeofday, "YY")) 	// get the current year
+	var/MM = text2num(time2text(world.timeofday, "MM")) 	// get the current month
+	var/DD = text2num(time2text(world.timeofday, "DD")) 	// get the current day
+
+	for(var/H in typesof(/datum/holiday) - /datum/holiday)
+		var/datum/holiday/holiday = new H()
+		if(holiday.shouldCelebrate(DD, MM, YY))
+			holiday.celebrate()
+			if(!holidays)
+				holidays = list()
+			holidays[holiday.name] = holiday
+
+	if(holidays)
+		holidays = shuffle(holidays)
+		world.update_status()