This reverts commit 92db97a26dbdd5c2210df39dd08a716faf6102f6.
There is no need to make this a static property because it can be added at runtime via Python or the GUI
The Original BaseFeature implementation had some serious issues with scoped links. It failed completely for e.g. sketches on the BaseFeature as it made a local link to refere to a out of body object. The only solution to make this work correctly is to add a proxy object into the body which is alloed to exactly that, to link outside oof the body. Something like shapebinder.
This is the first feature that used GeoFeatureGroupExtension and required links to the groups inside as well as to things on the same level. Hence a few modifications to link scopes have been nesseccary.
