- Fix row removal when applying a delete.
  In Gtk2, we could shove the iters of deleted rows into an array,
  and delete all row iters from the model at the end, which was faster
  than deleting them 1-by-1 ( I think ). This doesn't work in Gtk3.
  The iter becomes invalid. So now we delete iters from the model
  as we process the database deletes.

- Fix calling on_apply() for deletes. This was being called for everything
  APART from deletes.