Corrected headings level and anchor syntax

[pbuehler]

This streamlines the presentation of the "data model reference".

[pbuehler]

@vkucera There are still problems with the internal links. To replace "<h2 id=" by "<a name=" is obviously not sufficient to solve the issue. However, with this PR the headings levels should be improved. The modified python scripts, which produce the new layout will be provided in an extra PR to the O2 repo.

[vkucera]

@vkucera There are still problems with the internal links. To replace "<h2 id=" by "<a name=" is obviously not sufficient to solve the issue. However, with this PR the headings levels should be improved. The modified python scripts, which produce the new layout will be provided in an extra PR to the O2 repo.

Thanks, @pbuehler . Concerning the heading levels, I am thinking whether the workflow names should be at the third level everywhere to avoid blowing up the menu with the long list. See my comment AliceO2Group/AliceO2#10823 (comment)
For the internal links, I guess it's a limitation of markdown-link-check that we have to live with.

[pbuehler]

This concerns the helper tasks only, right? With he current number of tasks I think it is ok to have them listed in the menu.
Since the list in the menu fits onto one screen, it makes it easy to find and select a specific task and with this helps navigation. Should the number of tasks increase significantly in future we can revisit the situation.

[vkucera]

If the list fits on the screen, I am fine with it.