Reuse referencesitemapitem on sitemenu item

For the hst:referencesitemapitem of a sitemenu item, you can reuse the value of the parent item through ${parent}

Thus instead of

+ sitemenu
    + News
        - referencesitemapitem = 'news'
        + 2011
            - referencesitemapitem = 'news/2011'

you can use

+ sitemenu
    + News
        - referencesitemapitem = 'news'
        + 2011
            - referencesitemapitem = '${parent}/2011'