[IMP] documentation-user: restructuring submenu

— Layout

* Create html templates to print breadcrumb's and submenu's lists.
* Remove ‘o_main_back’ ( no longer needed)
* Minimum mobile support for submenu. Note: The default website submenu
should be refactored in order to support mobile by default

— Style

* Create a less mixin to handle all doc’s dropdowns
* Add a specific style for breadcrumb when it’s placed inside the
submenu.

_extensions/odoo/switchers_list.html

@@ -0,0 +1,25 @@
+{% if languages %}
+<li class="languages dropdown">
+    <a class="dropdown-toggle" href="#" data-toggle="dropdown">
+        {{ language }}
+    </a>
+    <ul class="dropdown-menu" role="menu">
+        {% for name, url in languages %}
+            <li><a href="{{ url }}">{{ name }}</a></li>
+        {% endfor %}
+    </ul>
+</li>
+{% endif %}
+
+{% if versions %}
+<li class="versions dropdown">
+    <a class="dropdown-toggle" href="#" data-toggle="dropdown">
+        {{ version }}
+    </a>
+    <ul class="dropdown-menu" role="menu">
+        {% for name, url in versions %}
+            <li><a href="{{ url }}">{{ name }}</a></li>
+        {% endfor %}
+    </ul>
+</li>
+{% endif %}