Reimplement and simplify Hugo's template system

See #13541 for details.

Fixes #13545
Fixes #13515
Closes #7964
Closes #13365
Closes #12988
Closes #4891

tpl/tplimpl/embedded/templates/_partials/disqus.html

@@ -5,7 +5,7 @@
     window.disqus_config = function () {
     {{with .Params.disqus_identifier }}this.page.identifier = '{{ . }}';{{end}}
     {{with .Params.disqus_title }}this.page.title = '{{ . }}';{{end}}
-    {{with .Params.disqus_url }}this.page.url = '{{ . | html  }}';{{end}}
+    {{with .Params.disqus_url }}this.page.url = '{{ . |  transform.HTMLEscape | safeURL }}';{{end}}
     };
     (function() {
         if (["localhost", "127.0.0.1"].indexOf(window.location.hostname) != -1) {

tpl/tplimpl/embedded/templates/_partials/pagination.html

@@ -20,7 +20,7 @@
 {{- if in $validFormats $format }}
   {{- if gt $page.Paginator.TotalPages 1 }}
     <ul class="pagination pagination-{{ $format }}">
-      {{- partial (printf "partials/inline/pagination/%s" $format) $page }}
+      {{- partial (printf "inline/pagination/%s" $format) $page }}
     </ul>
   {{- end }}
 {{- else }}