   Tree:
      (cnt . node)

   Node:
      (key less more . value)  # 3 cells
   e.g.
      (key {5555} {7777} . {1111})

   Max DB-Size: 7 digits -> 2**42 (10**12) Blocks (2**48 Bytes, 256 TB)
      <Link> BEG TRANSIENT <key> EXTERN <7> EXTERN <7> DOT EXTERN <7> NIX
      -> keyLen: 30  # 6+2+30+1+7+1+7+2+7+1 = 64


   +Key  ("key" less more . {obj})
   +Ref  (("key" . {obj}) less more . {obj})
   +Idx  (("key" {obj}) less more . {obj})
   +Sn  (("key" {obj} . T) less more . {obj})
