Translation problem with Bookcase 0.6.4

Ulf-Diether Ehlert pointed out to me in an email that a translation problem exists in Bookcase for the category titles for the default book collection. Rather than repeating all the i18n calls in constructing the default fields, I stuck them in a static const QString, but I failed to use I18N_NOOP. As I don’t use a translated version (maybe I should include that as a check when I put a release together), I never noticed the problem. It’s been there since Bookcase 0.6.1. Here’s a patch.