Page History

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1. Optional named parameters:
   mountPage("/page/${named1}/#{named2}", MyPage.class);
   This means the second parameter is optional. Requests to "/page/a/b" , "/page/a/b/" and "/page/a/" will be handled by MyPage and the parameters can be get with PageParameters.get(String) (e.g. parameters.get("named2") will return "b" for the first case and null for the second).
   The mapper is smart enough to handle optional named parameters in any segment, not just the last one.

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