“There has sometimes been a tendency to equiparate joint involvement in the crime with joint ownership of the fruits of the crime. But the fact that the defendants were jointly responsible for the crime in question does not automatically justify a conclusion that they jointly obtained the resulting property….judges in confiscation should be ready to investigate and made findings as to whether there were separate obtainings… A court should never make a finding that there has been joint obtaining from convenience, or worse from laziness”