anchor IDs should be section number

[emh789]

Problem:

Navigational <a> anchor elements in contents, topic, and subcontents blocks include the new unique topic id number. This leads to a semantic mismatch. For example, a link to section 5.2 might be coded as #text-main-67.

Proposal:

Use the section number for anchor ids.

[emh789]

This will be an opportunity to refactor methods relating to section number. Although it won't affect the experience of clicking navigation links or outlining a project, this will probably result in a quick Major Release upgrade, because it will require re-rendering a project for internal consistency.