Allow userInput fields to have a 'summaryKey' attribute. This will
indicate that you want some variable to be shown on the userInputPanel,
with a some key that is referenced in your langpacks. If the key is not
in your langpacks the key itself will be used.
Allow userInput panels to have a 'summaryKey' attribute. This will
indicate that you want to show a userInputPanel on the SummaryPanel.
Updating xsd for userinput
Merge pull request #190 from mtjandra/IZPACK-1081

[IZPACK-1081] - Summarize UserInputPanel Feature