Better Book navigation links

Description of the need

You're reading through Backdrop's User Guide, currently the Managing comments page. After you've read though the page, there's a handy link at the bottom to go to the next page. You find this helpful, as it saves having to scroll back up the long page to find the link to the next page. So you click the link and read through the Working with files page. Once at the bottom, you click the link to go the the next page (Contact forms).

However, you don't realise that you entirely missed the Managing file locations and access page! As a result, you don't setup file access properly, someone's able to view a private file, information gets leaked, governments topple, and the world ends.

Ok, so maybe it's not that dramatic, but it's not ideal that Book navigation currently skips over any sub-pages. Books are made to (more-or-less) be read in a systematic fashion (hence the navigation links at the bottom of each page). They don't currently do that as well as they could.

Proposed solution

Ideally, there'd be navigation links at the bottom of each page that take the user to the: - Next page - Previous page - Next section - Previous section

If we take the Modules page as an example, the new proposed links would point to: - Deep Dive: Manual Module Installation (next page) - Rules (previous page) - Themes (next section) - Contributed Modules (previous section)

I'm thinking the links could be laid out similar to how pager links are laid out. For example:

<< Contributed Modules     < Rules     Up     Deep Dive: Manual Module Installation >     Themes >>

But I'm open to suggestions on that point...