This is largely inspired by the excellent feedback we got from David
Welsch, although this patch is only a very early first step towards
where we want to be with the documentation.
First, I'm splitting the large administrator guide into several large
sections: features, operation, architecture. Some of their topic might
actually find a better home outside of the administrator guide, but I
don't go that far in this change.
Second, I'm grouping several separate things together with the larger
topics:
- API topics are relevant for users and are grouped with the user guide
- Configuration guide and release notes are grouped with the
administrator guide.
- The command reference is renamed for clarity and also grouped with the
administrator guide since these are not user-visible commands.
- I'm dropping the "Advanced topics" subsection. While I like its
intention (and I think it was me who added it in the first place),
it's clear that such separation makes these topics much less
discoverable.
Third, I'm playing with :maxdepth: here to make the sub-pages more
informative.
Change-Id: Icd0a35b252136b7da107c6346c48473cf1b99bcb
656f93b6e7