Disambiguate items in Related items listing

[fbennett]

The Related tab on an item currently shows the getDisplayTitle() string for each related item. As ​raised on the forums, in many common use cases for related items (book reviews, alternative editions, law cases) the title alone does not discriminate between the items, necessitating back-and-forth navigation to identify which source in the list is of interest.

The attached patch implements a disambiguated Related items listing, which is performing well in the multilingual branch. Here is a description of the algorithm (also outlined in the thread linked above).

Slots

• There are two label slots for each related item (one left- and one right-aligned).

Slot fillers

1. The author name always shows through in the first slot, if
   1. it is present; and
   2. it differs from the author of the current item.
2. Three other slot fillers are available (attempted in order):
   1. the title (or short title);
   2. a composite of volume, issue, and container title; and
   3. the date.
3. If 2.1 or 2.2 matches any other item in the listing, it is dropped, and the next info chunk is used instead.
4. If no info chunks are available (and useful for disambiguation), the first slot gets an empty label and the year goes in the last.