Qt Designer Form Class wizard resets class name (and associated header, source and form file names)

The Qt Designer Form Class wizard resets the class name, and the associated header, source and form file names, when going back from the "Project management" page to the "Choose a class name" page.

The class name should only be changed when going from the "Choose a form template" page to the "Choose a class name" page.

Arguably, this should also only happen if the user has not set an explicit class name, or file names, for the class. If the user changed any of the default names, the explicitly set names should be preserved for the lifetime of the wizard.