Drop dependency on PROOF/TDSet - remove GetDataset()
Remove our implementation ::GetDataset() which used to return TDSet. Let the TGridCollection::GetDataset() (super class) throw exception because this method shouldn't be used anyway.
Remove our implementation ::GetDataset() which used to return TDSet. Let the TGridCollection::GetDataset() (super class) throw exception because this method shouldn't be used anyway.