Changes all cases of update_icons(), updateicon(), UpdateIcon() etc. to update_icon(). (#9432)

update_icons(), UpdateIcon() and updateicon() are now changed to be update_icon().

Many interactions expect a target to have an update_icon(), so they should all be the same.

Also fixed some stuff that was using relative pathing, along the way.

code/modules/client/preferences.dm

@@ -462,7 +462,7 @@ datum/preferences
 		character.update_body(0)
 		character.update_hair(0)
 		character.update_underwear(0)
-		character.update_icons()
+		character.update_icon()
 
 /datum/preferences/proc/open_load_dialog_sql(mob/user)
 	var/dat = "<tt><center>"