Centralize all usages of System.identityHashCode()

Substitute all uses of System.identityHashCode() behind a method like this in Util:

public static String hexIdHashCode(Object o)

{ return Integer.toHexString(System.identityHashCode(o)); }

The hexadecimal version occupies less space and does the same job.

Also, stop/start marshaller should not print the id hash code, it's too verbose and it's only needed when debugging a particular problem which has not been present in a while.