Unable to determine if a parameter was received from the command line

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Due to a recent change for handling required parameters at:

https://github.com/cbeust/jcommander/commit/6436ca65881e658504652fc41d7a9a6e07df82a8#r132149657

it is no longer possible determine if a parameter was received from the command line. That information is useful independent of whether a parameter has a default value or not.