Reuse relativecontentpath from parent sitemap item

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

Thus instead of

+ sitemap
    + news
        - relativecontentpath = 'news'
        + _any_
            -relativecontentpath = 'news/${1}'

you can use

+ sitemap
    + news
        - relativecontentpath = 'news'
        + _any_
            -relativecontentpath = '${parent}/${1}'