Include all section levels in table of contents, provide anchors for all document sections

Currently the HTML flavor of the specification documents contains mostly section bookmarks of the form _Toc followed by a nine-digit number.

Also not all sections are listed in the table of contents, so referencing to a section on level 4 or 5 requires inspecting the generated HTML code of the specification.

This is not made easier by the fact that most sections have about a dozen of the _Tocnnnnnnnnn anchors instead of one memorable anchor.