Add 'settings' link to side menu on Admin's panel.

app/views/admin/_menu.html.erb

@@ -212,5 +212,12 @@
         </li>
       </ul>
     </li>
+
+    <li class="section-title <%= "active" if controller_name == "settings" %>">
+      <%= link_to admin_settings_path do %>
+        <span class="icon-settings"></span>
+        <strong><%= t("admin.settings.index.title") %></strong>
+      <% end %>
+    </li>
   </ul>
 </div>