Render HTML contained in messages

For some messages it is useful to render the HTML such as for example if
you have multiple messages and want to display them as list.

serveradmin/common/templates/base.html

@@ -58,7 +58,7 @@
     {% if messages %}
         {% for message in messages %}
             <div class="alert {{ message.level_tag|bootstrap_alert }} alert-dismissible fade show" role="alert">
-                <strong>{{ message }}</strong>
+                <strong>{{ message|safe }}</strong>
                 <button type="button" class="close" data-dismiss="alert" aria-label="Close">
                     <span aria-hidden="true">&times;</span>
                 </button>