This patch does three things:
First it enables multiple authors and series support. Series still has a bit of a downside that now the series carousel shows all books in the same series as the current book, but we'll just need to think about how to access other series.
Second, it enables reading/writing to and from the KFileMetaData ratings, tags and user comments. These have been integrated into the BookTile, and you can edit them from there. I didn't add these to the database, as it didn't seem sensible to cache these.
Finally, it adds 'description' from the default annotation.
I had to hide the comment/tags from the booktile in book.qml because the widget was too small.
Anyway, as I was modifying the category entries anyway, I figured doing the KFileMetaData stuff as well.