Add badge printing capabilities (#868)

Add badge printing capabilities

src/pretix/plugins/badges/forms.py

@@ -0,0 +1,32 @@
+from django import forms
+from django.utils.translation import ugettext_lazy as _
+
+from pretix.plugins.badges.models import BadgeItem, BadgeLayout
+
+
+class BadgeLayoutForm(forms.ModelForm):
+    class Meta:
+        model = BadgeLayout
+        fields = ('name',)
+
+
+class BadgeItemForm(forms.ModelForm):
+    class Meta:
+        model = BadgeItem
+        fields = ('layout',)
+
+    def __init__(self, *args, **kwargs):
+        event = kwargs.pop('event')
+        super().__init__(*args, **kwargs)
+        self.fields['layout'].label = _('Badge layout')
+        self.fields['layout'].queryset = event.badge_layouts.all()
+        self.fields['layout'].required = False
+
+    def save(self, commit=True):
+        if self.cleaned_data['layout'] is None:
+            if self.instance.pk:
+                self.instance.delete()
+            else:
+                return
+        else:
+            return super().save(commit=commit)