Improve Container API

RecoverableContainer<Sample> theContainer = new RecoverableContainer<Sample>();
Sample obj1 = theContainer.create(new SampleLockable(10));
Sample obj2 = theContainer.create(new SampleLockable(10));

// todo make it easier to create and share objects.

Make sharing of objects like this the default even for pessimistic. Just pass back the
same instance in that case. Also hide getUidForHandle by simply passing the obj instance.fr

Sample obj3 = theContainer.duplicate(obj1);
Sample obj4 = theContainer.duplicate(obj2);

but for duplicate to work, we'd need to create a new instance of SampleLockable, so it needs to have a default constructor. And even then, it needs to be transactional.