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*Release date: 30-Nov-2010*
* Fixed the bug where existing form data was not getting populated on a GET request.
* Updated the process of process_POST to not automatically call self.clear().
The developer of the wizard now should call self.clear() right before a
successful return from self.done(). If the wizard needs to redirect to a step
in the process because of post processing error then the SessionWizard will
not remove the data form session now.