Support copying of mutable objects in generated ValueObjects.

[amandel]

If a mutable object is stored in the value type a copy of an object must normally be stored and also generated when it is retrieved again, to avoid accidental modifications.

It should be possible for the generated ValueObjects? to support this pattern.

There are two common ways to copy objects in java. One is to use the clone method the other is realized through a copy constructor.

To support this a new attribute "copyValue" should be added to the member element. Possible values are clone or constructor. The type used must support the selected copy mechanism.