Vlad's throne rebalance

This removes the container-cursing effect (which is too specific
and too easy to work around) and replaces it with an effect that
greases everything (largely but not entirely positive).

src/apply.c

@@ -2583,6 +2583,8 @@ grease_ok(struct obj *obj)
     if (!obj)
         return GETOBJ_SUGGEST;
 
+    /* note: if changing the list of ungreasable objects, also change
+       special_throne_effect in sit.c */
     if (obj->oclass == COIN_CLASS)
         return GETOBJ_EXCLUDE;