make nested sub-categories show up in the layout template

flask_admin/templates/bootstrap2/admin/layout.html

@@ -22,23 +22,32 @@
       {%- if children %}
         {% set class_name = item.get_class_name() %}
         {%- if item.is_active(admin_view) %}
-        <li class="active dropdown">
+        <li class="active dropdown{% if class_name %} {{class_name}}{% endif %}">
         {% else -%}
-        <li class="dropdown">
+        <li class="dropdown{% if class_name %} {{class_name}}{% endif %}">
         {%- endif %}
           <a class="dropdown-toggle" data-toggle="dropdown" href="javascript:void(0)">
             {% if item.class_name %}<i class="{{ item.class_name }}"></i> {% endif %}{{ item.name }}<b class="caret"></b>
+            {{ menu_icon(item) }}{{ item.name }}
+            {%- if 'dropdown-submenu' not in class_name -%}<b class="caret"></b>{%- endif -%}
           </a>
           <ul class="dropdown-menu">
           {%- for child in children -%}
+            {%- if child.is_category() -%}
+              {{ menu(menu_root=[child]) }}
+            {% else %}
               {% set class_name = child.get_class_name() %}
               {%- if child.is_active(admin_view) %}
+              {{ child.is_active(admin_view) }}
               <li class="active{% if class_name %} {{class_name}}{% endif %}">
               {% else %}
               <li{% if class_name %} class="{{class_name}}"{% endif %}>
               {%- endif %}
-              <a href="{{ child.get_url() }}"{% if child.target %} target="{{ child.target }}"{% endif %}>{{ menu_icon(child) }}{{ child.name }}</a>
+              <a href="{{ child.get_url() }}"{% if child.target %}
+               target="{{ child.target }}"{% endif %}>
+              {{ menu_icon(child) }}{{ child.name }}</a>
               </li>
+            {%- endif %}
           {%- endfor %}
           </ul>
         </li>