Add variants feature

The variant feature provides a way to have content (full page or part of page's content) published conditionally.

This requires a macro for the page content.

A user interface displays a list of variants of the current book, with the following data for each;

• name
• button for deleting a variant
• a button to see a list of all pages related to the variant (being the whole page or having the macro)?

On top of this list, a button is provided to create a new variant.