[IZPACK-1093] SummaryPanel shows content of skipped and not relevant panels

This solves the problem of showing contents of skipped panels the user has never visited or that have been deactivated during a sequence of Back, new choices and new panel conditions in SummaryPanel.
Panels are marked visited now if they have been visited, all following panels are marked unvisited, depending on how the are defined in the <panels> section.

In relation to this fix there has been also made a cleanup how createForPack, createForUnselectedPack and os constraints are handled for UserInputPanels. Switching a panel from within activatePanel() has not been a good idea and messed up the AbstractPanels handling.