Implemented mod 16 addition
Removed confusing multiple key constructors, until further clarification
Implemented HexKeyUtil for HexKey-specific operations and logic that is detached from the HexKey implementation classes
Adjusted the DESKey constructor for a more consistent entry point,
Used the HexKeyUtil for adding keys, as opposed to the confusing multiple key constructor
Merge branch 'cvv'
[maven-release-plugin] prepare release hans-1.1