Change PODS from Q_OBJECT to Q_GADGET

This requires removing the notify signal from POD
Q_PROPERTY values.

Change-Id: I12da6aed4f0babef5bb90f6817da74573070d608
Reviewed-by: Continuous Integration (KDAB) <build@kdab.com>
Reviewed-by: Björn Breitmeyer <bjoern.breitmeyer@kdab.com>