Allow to control the path delimiter and create unknown datastructures

Also the labeling of form fields was improved

templates/parts/import/parts_import.html.twig

@@ -26,6 +26,11 @@
 {% endblock %}
 
 {% block card_content %}
+    <p class="text-muted offset-sm-3">
+        {% trans %}parts.import.help{% endtrans %}<br>
+        {% trans with {'%link%': 'https://docs.part-db.de/'} %}parts.import.help_documentation{% endtrans %}
+    </p>
+
     {{ form(import_form) }}
 
     {% if imported_entities %}