simplify achievement tracking for special objects

This turned out to be a lot more work than I anticipated, but it is
definitely simpler (other than having #wizmakemap take achievements
away if you replace the level that contains the 'prize', which wasn't
handled before).

I cheated and made Mine's End into a no-bones level because the new
flagging scheme for luckstone, bag, and amulet can't carry over from
one game to another.  It probably should have been no-bones all along.
Sokoban didn't have this issue because it's already no-bones.

Existing save files are invalidated.

dat/dungeon.lua

@@ -178,7 +178,8 @@ dungeon = {
          },
          {
             name = "minend",
-            bonetag = "E",
+--          3.7.0: minend changed to no-bones to simplify achievement tracking
+--          bonetag = "E"
             base = -1,
             nlevels = 3
          },