[docheinz] Hugo: replace .URL by .Permalink; update build instructions ()

hugo/config.toml

hugo/content/installation/building/unix/build-and-install.md

hugo/content/installation/building/unix/get-source.md

hugo/content/installation/building/unix/third-party.md

hugo/layouts/partials/breadcrumb2.html

hugo/layouts/partials/next-prev-page.html

hugo/layouts/partials/pagination.html

hugo/layouts/partials/sidebar.html

hugo/layouts/shortcodes/children.html

hugo/layouts/shortcodes/ref-py.html

hugo/layouts/shortcodes/relref.html

hugo/layouts/shortcodes/url-repo.html