This class is responsible for reacting to events generated by pushing any of the
three buttons, 'Next', 'Previous', and 'Cancel.' Based on what button is pressed,
the controller will update the model to show a new panel and reset the state of
the buttons as necessary.
This constructor accepts a reference to the Wizard component that created it,
which it uses to update the button components and access the WizardModel.
The model for the Wizard component, which tracks the text, icons, and enabled state
of each of the buttons, as well as the current panel that is displayed.