Removed duplicated code from the buildNav() function, where the version
of the code used is one where items are only written if they haven't
already been encountered, and a heading is only written when there are
items to appear beneath that heading.
Remove the 'module:' prefix from index links to classes and interfaces
defined within modules.
Ensure the title for classes defined within modules shows the thing
being documented as being a class rather than a module, as it currently
does for interfaces.