Add bulk update functionality for trainees from spreadsheet input

generic/templates/generic/trainees.html

@@ -11,6 +11,7 @@
     {% endfor %}
     (<a href="{% url 'create_trainee' %}" title="Click to add a trainee to the platform, creating an account for them.">Add trainee</a>)
     (<a href="{% url 'accounts_bulk_create' %}" title="Click to create multiple trainees at once.">Bulk create</a>)
+    (<a href="{% url 'trainees_bulk_update_from_spreadsheet' %}" title="Click to update multiple trainees at once.">Bulk update</a>)
 
     <h2>
         {% if grade %}