TT-7122 include General projects in burrito content folders

[gtryus]

Summary

• The Books step now records a General project's book key from its project default when no passage has a book, so that key is saved with the Scripture books.
• Audio, Text, Resources, Navigation, and Notes create a folder per saved book, so the General project is included there. Apm Data already included both projects by name.
• A Burrito Books component test selects a Scripture project (Genesis) and a General project whose passages have no book, and requires both names under Selected Books.

Test plan

• Export a burrito with both a Scripture project and a General project, and with Audio, Text, Resources, Navigation, Notes, and Apm Data selected.
• Apm Data still shows both project folders.
• Audio, Text, Resources, Navigation, and Notes each include the General book folder as well as the Scripture book folder.