Fast resume support for etorrent:

* First, we should get etorrent to understand that there are mnesia
  tables which are being disk-logged rather than being in RAM.

* Then we should construct a process which periodically checks the
  current state of torrents, builds their bitfields and adds them to
  the table that is disk-logged.

  - Every 5 minute we go through the #piece/#torrent/#tracking_map.

  - Build a bitfield for each.

  - Store the bitfield together with what torrent that bitfield is
    for.

  - Prune bitfields which has no torrents.

* Finally, the fs_checker should use this information when starting.

* And then, everything should be checked for odd errors.

Build a plan for adding fast resume support.
Build a plan for adding fast resume support.
