Replaces /image with /mutable_appearance (#556)

* Replaces /image with /mutable_appearance, where appropriate

* Update miscellaneous.dm

* Delete miscellaneous.dm.rej

* Delete pet.dm.rej

* Update pet.dm

* Update species.dm

* Update miscellaneous.dm

* Update species.dm

* Update miscellaneous.dm

* Delete species.dm.rej

* Update species.dm

pretty sure I got all the indentation correct THIS time, ffs

* Update species.dm

* Update species.dm

fucking tabs man, fucking tabs.

code/datums/mutable_appearance.dm

@@ -0,0 +1,18 @@
+// Mutable appearances are an inbuilt byond datastructure. Read the documentation on them by hitting F1 in DM.
+// Basically use them instead of images for overlays/underlays and when changing an object's appearance if you're doing so with any regularity.
+// Unless you need the overlay/underlay to have a different direction than the base object. Then you have to use an image due to a bug.
+
+// Mutable appearances are children of images, just so you know.
+
+/mutable_appearance/New()
+	..()
+	plane = FLOAT_PLANE // No clue why this is 0 by default yet images are on FLOAT_PLANE
+						// And yes this does have to be in the constructor, BYOND ignores it if you set it as a normal var
+
+// Helper similar to image()
+/proc/mutable_appearance(icon, icon_state = "", layer = FLOAT_LAYER)
+	var/mutable_appearance/MA = new()
+	MA.icon = icon
+	MA.icon_state = icon_state
+	MA.layer = layer
+	return MA