Add option to show failed files in torrent verify subcommand

Hi,

when running something like this:

```imdl torrent verify -i mytorrent.torrent -c /data/torrentcontent/```

imdl is only able to say that the verification had success or pieces have failed.

I would like to have an option to get a report which files failed. Like in the situation where files are missing (they get shown).

For example this:

```imdl torrent verify -r -i mytorrent.torrent -c /data/mytorrentdata/``` (-r means e.g. report)

Should be able to say something like this (when files fail):

```File XXXXXX failed (piece X-Z)```

This is e.g. helpful for torrents which contain a directory. Aspecially when they are hugh so a single file can be replaced to fix the issue if possible. Actually you will not find the file with imdl. You just know womething is wrong.

Best Regards