JORTE: don't use finalizers in Java classes

JORTE: don't use finalizers in Java classes

This replaces finalizers with explicit destroy() functions, because the
order in which objects with no reference in the VM are garbage-collected
is not guaranteed. This caused trouble with finalization of DomainApp
and Publisher (or Subscriber). If the DomainApp was destroyed before
the Publisher (or Subscriber) the Publisher's finalizer would have been
stuck (eventually leading to TimeoutException to be thrown).