Navigation tree depth is limited

[Rbiessy]

The depth of the navigation tree on the left seems to be limited to 3 levels. The sparse blas domain could use a 4th level so that the functions under the "Data handles" page are more easily accessible.
The html page does not allow to expand the "Data handles" page but my local html build does, see the image below and the html build: docs.zip

The issue was partially discussed in #588 and the PR #597 was not enough to fix it.

[iMartyan]

+1 for the issue
Same applies for oneMath RNG domain, which is unreadable with current drop down list depth.
I've tried to change :maxdepth: in index files but somehow it only affects partial build of single domain, and whole spec build remains the same

[rscohn2]

If I had to do it all over again, I would not make a single document, I would make each spec a separate document. There could still be some top level navigation between specs. This would fix the navigation problem. Since it is already possible to build a spec as a standalone document, spec owners would not need to do anything--the work would be in the publishing scripts.

I am not even sure we need to have a common release schedule or a common site for publishing, but that would be a bigger step and put more of the burden on the individual projects.