Fix event wizard date picker (remove dependency)

• Use plain html functionality instead of bootstrap datepicker.
• Remove datepicker dependency.
• This resolves #200 (closed) (datepicker not loading since load from CDN is blocked by CSP).
• Improve how form media is loaded in event wizard.
• Additionally, improve which fields are shown (and how) in event wizard.

AKModel/templates/admin/AKModel/event_wizard/activate.html

@@ -8,6 +8,11 @@
 
 {% block title %}{% trans "New event wizard" %}: {{ wizard_step_text }}{% endblock %}
 
+{% block extrahead %}
+    {{ block.super }}
+    {{ form.media }}
+{% endblock %}
+
 {% block content %}
     {% include "admin/AKModel/event_wizard/wizard_steps.html" %}
 
@@ -17,8 +22,6 @@
 
     <h5 class="mb-3">{% trans "Successfully imported.<br><br>Do you want to activate your event now?" %}</h5>
 
-    {{ form.media }}
-
     <form method="post">{% csrf_token %}
         {% bootstrap_form form %}