This commit enables the generation and display of the ToC on all pages
where it's relevant due to the content size.

More pages could have been included but left aside due to inconsistent
use of heading levels leading to rendering/visual glitches.

The pages' content has not been modified, except for the "Terms of use"
page which included a manually-generated ToC.

Signed-off-by: Arnaud Ferraris <arnaud.ferraris@collabora.com>