Some plane tweaks.

-Defines a new plane for things that are above objects without casting shadows on fake ao.
-Moves a bunch of effects that aren't supposed to cast shadows on planes that don't cast shadows.
-Also tweaks these things for some other things, such as cliffs and resting prottie blobs.

code/game/objects/structures/cliff.dm

@@ -34,6 +34,7 @@ two tiles on initialization, and which way a cliff is facing may change during m
 	climbable = TRUE
 	climb_delay = 10 SECONDS
 	block_turf_edges = TRUE // Don't want turf edges popping up from the cliff edge.
+	plane = TURF_PLANE
 
 	var/icon_variant = null // Used to make cliffs less repeative by having a selection of sprites to display.
 	var/corner = FALSE // Used for icon things.