Sidebar matches new help docs structure

We've done a big re-layout of the structure of pages in gnome-user-docs,
update our sidebar links to point to the new top level elements and properly
match names with the actual articles
[endlessm/eos-shell#3910]
Merge pull request #20 from endlessm/shell/3910

Sidebar matches new help docs structure

[endlessm/eos-shell#3910]