Unify plural names of books

[Qrox]

Summary

SUMMARY: None

Purpose of change

Currently the plural names of books do not follow a clear convention. This PR aims to fix that and set a consistent convention for plural names of books.

Describe the solution

The proposed convention was added to JSON_INFO.md and the plural names of books were updated accordingly.

1. For non-periodical books (textbooks, manuals, spellbooks, etc.),
   1. If the book's singular name is a proper name, then the plural name is copies of (singular name). For example, the plural name of Lessons for the Novice Bowhunter is copies of Lessons for the Novice Bowhunter.
   2. Otherwise, the plural name is the usual plural of the singular name. For example, the plural name of tactical baton defense manual is tactical baton defense manuals
2. For periodicals (magazines and journals),
   1. If the periodical's singular name is a proper name, and doesn't end with "Magazine", "Weekly", "Monthly", etc., the plural name is issues of (singular name). For example, the plural name of Archery for Kids is issues of Archery for Kids.
   2. Otherwise, the periodical's plural name is the usual plural of the singular name. For example, the plural name of Crafty Crafter's Quarterly is Crafty Crafter's Quarterlies.
3. For board games (represented internally as book items),
   1. If the board game's singular name is a proper name, the plural is sets of (singular name). For example, the plural name of Picturesque is sets of Picturesque.
   2. Otherwise the plural name is the usual plural. For example, the plural of deck of cards is decks of cards.