title: Cached QSqlQueryModel to mimic OnManualSubmit
body: <p>I would like to implement a feature like the EditStrategy available on the QSqlTableModel but on a QSqlQueryModel because I have complex queries. </p>
  
  <p>I have already created my subclass of QSqlQueryModel implementing the <code>setData()</code> following the documentation and various examples. However I would like have a feature like the <code>OnManualSubmit</code> strategy available on the QSqlTableModel class. </p>
  
  <p>Any idea how to implement this caching? I also need to have the cached changes available in other view.</p>