Implement SSatoms

* Moves proc/initialize() from being on /atom/movable, /are and /turf/simulated to being on /atom - Now turfs can initialize too
* Added the SSatoms subsystem which controls initialization of atoms at roundstart and during normal conditions.
* Disabled the old auto_init = 0 behavior, ALL atoms should get initialized() called on them now.
* Refactored the way initialize() is called during /New() to utilize SSatoms instead of SScreation
* Removed SScreation, as it was only a stop-gap until SSatoms could be ported.
* Updated the maploader to inform SSatoms when it is loading maps instead of SScreation.
* Updated the template map loader to use SSatoms to perform initTemplateBounds
* Renamed 'initialized' var in seed_storage to deconflict.
* Removed usage of auto_init = 0, replaced with a no-op initialize() proc for atoms that don't need initialization.

code/modules/lighting/lighting_overlay.dm

@@ -10,7 +10,7 @@
 	//invisibility = INVISIBILITY_LIGHTING
 	color = LIGHTING_BASE_MATRIX
 	icon_state = "light1"
-	auto_init = 0 // doesn't need special init
+	//auto_init = 0 // doesn't need special init
 	blend_mode = BLEND_OVERLAY
 
 	var/lum_r = 0
@@ -19,6 +19,11 @@
 
 	var/needs_update = FALSE
 
+/atom/movable/lighting_overlay/initialize()
+	// doesn't need special init
+	initialized = TRUE
+	return INITIALIZE_HINT_NORMAL
+
 /atom/movable/lighting_overlay/New(var/atom/loc, var/no_update = FALSE)
 	. = ..()
 	verbs.Cut()