Fix zend navigation

The view helpers' documentation structure was changed from:

<pre>
    Zend\Navigation
        ...
        View Helpers
            Translation of labels and titles
            Integration with ACL
            Navigation setup used in examples
        View Helper - Breadcrumbs
        View Helper - Links
        View Helper - Menu
        View Helper - Sitemap
        View Helper - Navigation Proxy
</pre>

to:

<pre>
    Zend\Navigation
        ...
        Navigation View Helpers
            Translation of labels and titles
            Integration with ACL
            Navigation setup used in examples
            Included View Helpers
                Breadcrumbs Helper
                Links Helper
                Menu Helper
                Navigation Proxy Helper
                Sitemap Helper
</pre>