Ports baystation character preview system (#2630)

Ports the bay's character preview system, which is far better to observe aesthetic changes in the character creation, also solves the issues such as markings don't showing up at the character selection menu.

code/controllers/subsystems/mob.dm

@@ -9,6 +9,7 @@
 
 	var/list/currentrun = list()
 	var/list/all_mice = list()	// Contains all *living* mice.
+	var/list/mannequins = list()	//Contains all mannequins used by character preview
 
 /datum/controller/subsystem/mobs/New()
 	NEW_SS_GLOBAL(SSmob)
@@ -48,3 +49,9 @@
 
 		if (MC_TICK_CHECK)
 			return
+
+/datum/controller/subsystem/mobs/proc/get_mannequin(ckey)
+	. = mannequins[ckey]
+	if (!.)
+		. = new /mob/living/carbon/human/dummy/mannequin
+		mannequins[ckey] = .