#86 Revocation edit

* adds support for revocation edit
    * revocation document files will be replaced on an edit

konova/models/document.py

@@ -101,3 +101,19 @@ class AbstractDocument(BaseResource):
     def is_file_size_valid(cls, _file):
         max_size = cls._maximum_file_size * pow(1000, 2)
         return _file.size <= max_size
+
+    def replace_file(self, new_file):
+        """ Replaces the old file on the hard drive with the new one
+
+        Args:
+            new_file (File): The new file
+
+        Returns:
+
+        """
+        try:
+            os.remove(self.file.file.name)
+        except FileNotFoundError:
+            pass
+        self.file = new_file
+        self.save()