Performs a deep clone of this object. 

Returns a SmartPointer to the newly created clone, and adds a record to the specified ID map. 

If the cloning operation fails, a null SmartPointer is returned. 

A deep clone is a clone of this object and everything it owns. 

This function should not be called by client code; use OdDgDatabase::deepCloneObjects() instead. 

This function can be overridden in custom classes. 

The default implementation of this function appends the cloned object to the specified owner object.