Restore names of uploaded files on submit/draft restore (#65)

This involved turning the list of file IDs stored in the hidden
text field into JSON.

apps/files/models.py

@@ -19,6 +19,9 @@ class BaseFile(models.Model):
     def __str__(self):
         return self.file.name
 
+    def name(self):
+        return self.file.name
+
 
 class File(BaseFile):
     pass