Configurable disambiguator display in importer album overview

Currently, a tagging source prints some information about the found release in a predetermined layout, for example

```
URL:
http://www.discogs.com/Noisia-Spinor-Masada-Lifeless/release/354669
(Similarity: 51.7%) (album, artist, source, tracks) (Discogs, 2xVinyl, 2004, Netherlands, Citrus Recordings)
```

It would be very useful to be able to customize that layout. In my case, the simple addition of printing the catalog number of the found release would spare me looking at 2+ links per release.

Start at the importer album overview and trace how the tagging source assembles the displayed release information. Review the current fixed layout and identify how a configurable format could expose fields such as the catalog number. Done means users can customize the disambiguator display while retaining the existing information by default.

Written by the indexing model from the issue text.