Support +/- expand/contract in Book navigation on Drupal.org

Problem/Motivation

As part of
#1289090: [meta] Improve search/navigation for d.o community docs →
we reached consensus that we would like to add +/- "MSDN classic" style navigation to the right sidebar book navigation on Documentation pages on Drupal.org. This would allow people to drill down through the book without incurring page loads. An example of what this looks like on MSDN:

Proposed resolution

Develop or locate a module that adds this to the navigation if JavaScript is enabled, and degrades gracefully back to the current navigation if JavaScript is not enabled. The solution also needs to pass review by our Drupal Usabilty and Accessibility teams.

One possible module to test out: http://drupal.org/project/advancedbookblocks

Remaining tasks

1. Test the Advanced Book Blocks module to see if it will work with our existing very large book structures, and to verify that it is accessible and usable.
2. If so, get it deployed on Drupal.org, and someone will also need to consider a Drupal 7 port of that module very soon.
3. If not, develop a new module, for Drupal 6/7, that does what we need.

User interface changes

Visitors to the Drupal.org Community Documentation will be able to navigate through the book hierarchy without incurring page loads. They will be able to click +/- (or something like that) to expand/contract sections of the book hierarchy and find the pages they are interested in.

API changes

None.