Fix home page link for adding accounts

In our spreadsheet we had a page titled "How do I add more user accounts?"
that listed its page file as user-accounts.

But that page is about online accounts so I assume that was a type,
switched to user-add.page
[endlessm/eos-shell#4235]
Allow pages to have different titles on different guides

With the links attribute role, pages can have different titles
that targer differing roles.

A bit verbose, but I couldn't figure out a better way to do it.
[endlessm/eos-shell#4235]
Add home page titles for three pages

We decided to cut a few of our getting started stub pages and just
link pages from user-docs instead.

On the home page everything should appear as a question
[endlessm/eos-shell#4235]
Merge pull request #12 from endlessm/shell/4235

Shell/4235