Node.shouldStoreDeep: restore accidentally removed return statement

Regression by a62d4e130d543c14c203fa12600d1ecfb0c9fc8c
add a findbugs target to ant
Turn off findbugs by default. It's not even packaged in debian, so most devs won't have it.
Default target should be "package", revert previous commit.
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.
Some explanations about db4o, its problems, why they are largely our fault, what we can do about it.
Fix shadowing variable causing NPE when migrating.
Fix dangerous variable name shadowing.
Comments: This can happen, unfortunately. See the package docs.
Fix toString on arrays (client layer, thanks findbugs)
Delete dead/useless code (from findbugs). No effect.
Factor out crude US-ASCII check and don't rely on default charset (which might not be ascii-based)
Better US-ASCII check.