Fix/workaround some clone()-but-not-Cloneable warnings from FindBugs.
Make HashResult byte[] private, and provide a hashAsHex() method. (There was probably a warning about this)
Use Cloneable (after prev commit).
Make byte[] fields protected
Encapsulate USK.pubKeyHash properly.
Cloneable with FIXMEs
Cloneable
RunningAverage's are synchronized in clone(), fix one case, document, fix Cloneable warning.