Extend python interface for groups and fix test cases

src/Mod/PartDesign/App/Body.cpp

@@ -283,6 +283,9 @@ std::vector<App::DocumentObject*> Body::addObject(App::DocumentObject *feature)
     if (isSolidFeature(feature)) {
         Tip.setValue (feature);
     }
+    
+    std::vector<App::DocumentObject*> result = {feature};
+    return result;
 }
 
 
@@ -380,6 +383,8 @@ std::vector<App::DocumentObject*> Body::removeObject(App::DocumentObject* featur
         model.erase(it);
         Group.setValues(model);
     }
+    std::vector<App::DocumentObject*> result = {feature};
+    return result;
 }