Repository of schemas for scuttle-book

This repository contains the schemas used by scuttle-book. Both the
schema used in patch-book (v1)
and scuttle-book (v2).

Differences between v1 and v2

Subjective attributes: review, rating, ratingMax, ratingType, shelves,
genres have been added to the book structure directly so that they can
be used right away.

Futhermore:
- authors can be an array
- images can be an array
- shelves can be an array
- genres can be an array

About type is no longer used. Instead bookclubUpdate is
used. Similarly for comments where bookclubComment is used instead
of post.