Make PartDesign::Boolean work with new Link structure

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.

src/Mod/Part/App/BodyBase.cpp

@@ -41,6 +41,8 @@ PROPERTY_SOURCE_WITH_EXTENSIONS(Part::BodyBase, Part::Feature)
 BodyBase::BodyBase()
 {
     ADD_PROPERTY(Tip         , (0) );
+    Tip.setScope(App::LinkScope::Child);
+    
     ADD_PROPERTY(BaseFeature , (0) );
     
     App::OriginGroupExtension::initExtension(this);