[collector] can now collect Teile and list them

If a newly entered Teil already exists, we ignore that and do nothing.

"name" could become a primary key...

collector/templates/collector/index.html

@@ -15,3 +15,9 @@
   <p>Keine Teile da.</p>
 
 {% endif %}
+
+<form method="POST" action="{% url 'collector:enter' %}">
+  {% csrf_token %}
+  <input type="text" name="new_name" value="">
+  <input type="submit" name="submit" value="add new Teil">
+</form>