The Wizard is a nested UI-focused structure. The outer-most layer is
the WizardContainer a class that extends JPanel, and can therefore
be inserted into any other Swing widget (such as a JDialog or
JFrame). WizardContainer contains the four buttons ("< Prev"
"Next >" "Finish" and "Cancel") and a PageTemplate.
PageTemplate is another JPanel class that can be customized to add
wrapper widgets around the actual wizard dialog content. The default
PageTemplate does nothing but show the specified WizardPagees.
This default PageTemplate (DefaultPageTemplate) can be nested in
custom PageTemplates to easily reuse the logic needed to flip between
pages when adding wrapper content.