Includes:
- Avoid page break between a node and its borders
- Allow building an alternative TOC from document headings
On CRE documents, allows toggling between original TOC and an
alternative TOC with long-press on the "Table of content" menu
item.
Also update the Wikipedia stylesheet to further avoid
page-breaks between images and their caption, so a full
bordered wikipedia thumbnail is always full on a single page.
text=_("The table of content for this book is currently an alternative one built from the document headings.\nDo you want to get back the original table of content? (The book will be reloaded.)"),