[Intervention] Revocations files optional #4

* makes revocation file upload optional
 * adds overview about revocations to intervention index
 * adds/updates translations

intervention/forms.py

@@ -332,6 +332,7 @@ class NewRevocationForm(BaseModalForm):
     file = forms.FileField(
         label=_("Document"),
         label_suffix=_(""),
+        required=False,
         help_text=_("Must be smaller than 15 Mb"),
         widget=forms.FileInput(
             attrs={
@@ -371,12 +372,15 @@ class NewRevocationForm(BaseModalForm):
                 user=self.user,
                 action=UserAction.EDITED
             )
-            document = Document.objects.create(
-                title="revocation_of_{}".format(self.instance.identifier),
-                date_of_creation=self.cleaned_data["date"],
-                comment=self.cleaned_data["comment"],
-                file=self.cleaned_data["file"],
-            )
+            if self.cleaned_data["file"]:
+                document = Document.objects.create(
+                    title="revocation_of_{}".format(self.instance.identifier),
+                    date_of_creation=self.cleaned_data["date"],
+                    comment=self.cleaned_data["comment"],
+                    file=self.cleaned_data["file"],
+                )
+            else:
+                document = None
             revocation = Revocation.objects.create(
                 date=self.cleaned_data["date"],
                 comment=self.cleaned_data["comment"],