Show form elements for templates and folders

This commit adds:
- checkboxes to let you select a template or folder
- radio buttons to let you select where to move those template(s) and/or
  folder(s) to

It only does the `get` part of this work; handling the `post` and
calling API will be done in a subsequent commit.

app/models/service.py

@@ -325,3 +325,9 @@ class Service():
             path.append(folder)
 
         return list(reversed(path))
+
+    def get_template_folders_and_templates(self, template_type, template_folder_id):
+        return (
+            self.get_templates(template_type, template_folder_id) +
+            self.get_template_folders(template_folder_id)
+        )