Make _template an actual <template>, for correctness.

Author: kevinpschaaf

src/lib/template/templatizer.html

@@ -198,10 +198,10 @@
     },
 
     _customPrepAnnotations: function(archetype, template) {
-      // Don't store the actual template instance to avoid leaking; just
-      // store an object referencing its content
-      archetype._template = {_content: template._content};
-      var c = template._content;
+      // Store a "clone" of the template on the archetype (content has been
+      // pulled into _content property, so copy that also)
+      var t = archetype._template = document.createElement('template');
+      var c = t._content = template._content;
       if (!c._notes) {
         var rootDataHost = archetype._rootDataHost;
         if (rootDataHost) {