title: Show other data in QTableView with QItemDelegate
body: <p>I have a QTableView connected with an QSqlTableModel.<br>
  In the first column, there are only dates at this format: <code>2010-01-02</code><br>
  I want this column to show the date at this format (but without changing the real data): <code>02.01.2010</code><br>
  I know that I have to create an QItemDelegate for this column, but I don't know how I can read the existing data and overwrite it with something different. You have any idea how to manage that?</p>