Fix hint-problem tab bug TNL-2542

Revert the removal of hint templates.
Move the 'tab' attribute in the new-problem yaml
files out one level, out of the 'metadata' section.

cms/djangoapps/contentstore/views/component.py

@@ -282,8 +282,8 @@ def get_component_templates(courselike, library=False):
                     tab = 'common'
                     if template['metadata'].get('markdown') is None:
                         tab = 'advanced'
-                    # Then the problem can override that with a tab: setting
-                    tab = template['metadata'].get('tab', tab)
+                    # Then the problem can override that with a tab: attribute (note: not nested in metadata)
+                    tab = template.get('tab', tab)
 
                     templates_for_category.append(
                         create_template_dict(

cms/templates/js/add-xblock-component-menu-problem.underscore

@@ -3,6 +3,9 @@
         <li class="current">
             <a class="link-tab" href="#tab1"><%= gettext("Common Problem Types") %></a>
         </li>
+        <li>
+            <a class="link-tab" href="#tab2"><%= gettext("Common Problems with Hints and Feedback") %></a>
+        </li>
         <li>
             <a class="link-tab" href="#tab3"><%= gettext("Advanced") %></a>
         </li>