title: QAbstractTableModel: index() vs. createIndex()
body: <p>When subclassing QAbstractTableModel, what's the proper way to get a QModelIndex for a given row and column (for example, to provide a convenience method data(int row, int column))?</p>
  
  <p>There's index() and createIndex() - they both seem to do that?</p>
  
  <p>Example:</p>
  
  <pre><code>TableModel::data(int row, int column, int role) const
  {
      return data(index(row, column), role);
  }
  </code></pre>