Collection instances of ToJava and FromJava should have ToJava and FromJavaconstraints on the element types

[stephentetley]

Collection instances of ToJava and FromJava should have ToJava and FromJavaconstraints on the element types.

This will need the underlying implementations in Adaptor changing too.

Please assign to me.

[mlutze]

Maybe native types should automatically have a ToJava instance that is just the identity function. Otherwise manipulating collections of Java types could become difficult as everything needs a trivial instance (which I think the orphan rules don't allow)