Refactor templates to be more structured

templates/base/single.column.html.twig

@@ -0,0 +1,10 @@
+{% extends 'base/container.html.twig' %}
+
+{% block container %}
+    <div class="row">
+        <div class="col-sm mx-auto">
+            {% if title is defined %}<h3>{{ title }}</h3>{% endif %}
+            {% block body %}{% endblock %}
+        </div>
+    </div>
+{% endblock %}