move transfers into sqlitedict

oml/item/api.py

@@ -271,11 +271,9 @@ def cancelDownloads(data):
     ids = data['ids']
     if ids:
         for item in models.Item.query.filter(models.Item.id.in_(ids)):
-            t = models.Transfer.get(item.id)
+            t = state.downloads.transfers.get(item.id)
             if t:
-                t.progress = None
-                t.added = None
-                t.save()
+                del state.downloads.transfers[item.id]
             p = state.user()
             if p in item.users:
                 item.users.remove(p)