unoawt: completely separated the controller functionality of a wizard page from the wizard page itself,
by moving the canAdvance method from OWizardPage to the IWizardPage interface, which in this course has
been renamed to IWizardPageController.
This will later on allow to have implementations where the TabPage is provided by an external component
(e.g. as UNO Service), but the controlling of those pages is still intercepted and handled internally.