Selection feature bug with multiple extensions

If you have two extensions that extends the same class (like CCTV extends general publication), and then in selection feature selects to just generate one of them will not be reflected in the schema. If you do the _XXExtensionType will have all "children" independent if they were selected or not. This leads to that a not valid schema is created.

Solution is to add a additional check when generating the _XXXExtensionType, if class should be generated or not.