Add sub-events and relative date settings (#503)

* Data model

* little crud

* SubEventItemForm etc

* Drop SubEventItem.active, quota editor

* Fix failing tests

* First frontend stuff

* Addons form stuff

* Quota calculation

* net price display on EventIndex

* Add tests, solve some bugs

* Correct quota selection in more places, consolidate pricing logic

* Fix failing quota tests

* Fix TypeError

* Add tests for checkout

* Fixed a bug in QuotaForm

* Prevent immutable cart if a quota was removed from an item

* Add tests for pricing

* Handle waiting list

* Filter in check-in list

* Fixed import lost in rebase

* Fix waiting list widget

* Voucher management

* Voucher redemption

* Fix broken tests

* Add subevents to OrderChangeManager

* Create a subevent during event creation

* Fix bulk voucher creation

* Introduce subevent.active

* Copy from for subevents

* Show active in list

* ICal download for subevents

* Check start and end of presale

* Failing tests / show cart logic

* Test

* Rebase migrations

* REST API integration of sub-events

* Integrate quota calculation into the traditional quota form

* Make subevent argument to add_position optional

* Log-display foo

* pretixdroid and subevents

* Filter by subevent

* Add more tests

* Some mor tests

* Rebase fixes

* More tests

* Relative dates

* Restrict selection in relative datetime widgets

* Filter subevent list

* Re-label has_subevents

* Rebase fixes, subevents in calendar view

* Performance and caching issues

* Refactor calendar templates

* Permission tests

* Calendar fixes and month selection

* subevent selection

* Rename subevents to dates

* Add tests for calendar views

src/pretix/control/templates/pretixcontrol/subevents/delete.html

@@ -0,0 +1,19 @@
+{% extends "pretixcontrol/event/base.html" %}
+{% load i18n %}
+{% load bootstrap3 %}
+{% block title %}{% trans "Delete date" context "subevent" %}{% endblock %}
+{% block content %}
+    <h1>{% trans "Delete date" context "subevent" %}</h1>
+    <form action="" method="post" class="form-horizontal">
+        {% csrf_token %}
+        <p>{% blocktrans %}Are you sure you want to delete the date <strong>{{ subevent }}</strong>?{% endblocktrans %}</p>
+        <div class="form-group submit-group">
+            <a href="{% url "control:event.vouchers" organizer=request.event.organizer.slug event=request.event.slug %}" class="btn btn-default btn-cancel">
+                {% trans "Cancel" %}
+            </a>
+            <button type="submit" class="btn btn-danger btn-save">
+                {% trans "Delete" %}
+            </button>
+        </div>
+    </form>
+{% endblock %}