Avoid converting nested entity view objects if not needed

[beikov]

When converting a view AView which declares and attribute b of type BEditView with an attribute c of type CView, the object for the attribute b is converted to the BEditView type if a subtype e.g. BCreateView is encountered.

The problem now is, that we also convert c to CView again. We should try to avoid nested conversion if unnecessary. There should probably be a convert option though, to force the conversion.