model.BaseCRUD: don't define `url` in class; fix undefined `cfg`
model.BaseCRUD: don't define `url` in class; fix undefined `cfg`

* first saves memory when models are oprated thru store
* second had blown up inside proxy reader when loading data from backend
  silently thus gave a clue to listen to proxy exceptions

olecom/enjsms,olecom/enjsms