updated frontend stack to latest versions (#729)

templates/bundles/FOSUserBundle/Security/login.html.twig

@@ -3,16 +3,15 @@
 {% block logo_login %}{% include 'partials/logo_login.html.twig' %}{% endblock %}
 {% block title %}{{- get_title() -}}{% endblock %}
 
-{% block login_box_icon %}
-    <span class="glyphicon glyphicon-user"></span>
-{% endblock %}
-
 {% block head %}
     {{ parent() }}
     {% include 'partials/head.html.twig' %}
 {% endblock %}
 
 {% block stylesheets %}
-    {# we do not call parent() as we use a custom built for the frontend assets and don't want the default <stylesheet> #}
-    <link rel="stylesheet" href="{{ asset('build/app.css') }}">
+    {{ encore_entry_link_tags('app') }}
 {% endblock %}
+
+{% block javascripts %}
+    {{ encore_entry_script_tags('app') }}
+{% endblock %}