Fix #515 -- Add check-in lists (#693)

* Data model and migration

* Some backwards compatibility

* CRUD for checkin lists

* Show and perform checkins

* Correct numbers in table and dashboard widget

* event creation and cloning

* Allow to link specific exports and pass options per query

* Play with the CSV export

* PDF export

* Collapse exports by default

* Improve PDF exporter

* Addon stuff

* Subevent stuff, pretixdroid tests

* pretixdroid tests

* Add CRUD API

* Test compatibility

* Fix test

* DB-independent sorting behavior

* Add CRUD and coyp tests

* Re-enable pretixdroid plugin

* pretixdroid config

* Tests & fixes

src/pretix/control/forms/checkin.py

@@ -0,0 +1,31 @@
+from django import forms
+
+from pretix.base.models.checkin import CheckinList
+
+
+class CheckinListForm(forms.ModelForm):
+    def __init__(self, **kwargs):
+        self.event = kwargs.pop('event')
+        kwargs.pop('locales', None)
+        super().__init__(**kwargs)
+        self.fields['limit_products'].queryset = self.event.items.all()
+        if self.event.has_subevents:
+            self.fields['subevent'].queryset = self.event.subevents.all()
+            self.fields['subevent'].required = True
+        else:
+            del self.fields['subevent']
+
+    class Meta:
+        model = CheckinList
+        localized_fields = '__all__'
+        fields = [
+            'name',
+            'all_products',
+            'limit_products',
+            'subevent'
+        ]
+        widgets = {
+            'limit_products': forms.CheckboxSelectMultiple(attrs={
+                'data-inverse-dependency': '<[name$=all_products]'
+            }),
+        }