Refactoring: single place for random code generation

[Alexander Obuhovich]

In-Portal has interesting method, that is used to generated random codes. For example it's used for session id generation.

Because this method is located in Session class it can't be used in other places due it's visibility. I'm proposing to move this method to kUtil class. 

Task: http://tracker.in-portal.org/view.php?id=1376

Ready for testing.

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Best Regards,

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