Ticket #955, chapter types. Register taxonomy, insert three generic chapter types, create chapter_type function that fetches types for export.
Further adjustments to chapter types. Classes now added to webbooks. Activation functions in place.
Export templates.
Added front matter, back matter and chapter type classes for TOC.
Introduced new generics shortcode.
Allow more complex generic short codes based on $key => $value pairs.
Fixed bug with textbox shortcode.
Fixed export issue with #955.
Advanced settings section for chapter types. Ensure that chapter types are inserted when chapter types are enabled.
Make sure we re-insert default chapter types in case they have been customized.