Part: changes to Part Module

* Added Part::Feature::getTopoShape/getShape() function that can obtain
  shape from any object with proper implementation of getSubObject(). It
  can even construct compound from group object with proper implementation
  of getSubObjects().

* Modified ViewProviderExt to work on any object, because it now obtain
  the shape using Part::Feature::getShape()

* Modified various Part features to obtain base/tool shapes using
  Part::getShape(), which allows them to be any type of object,
  including Link and groups.

* Modified various Part command to relax type requirement on selected
  objects.

* Add support of link and group to dimension, and add dimension refresh
  command

* Support link and group in simple command command, and add a few more
  copy command variations.

* Add special handling of 'Shape' attribute in PropertyContainerPy and
  use Part::Feature::getShape() to return shape for any object without
  Shape property. This allows many python feature work with any object
  without modification.

* GeometrySurface/CurvePy, add convenience attribute 'Rotation'

* TopoShapePy:

    * Extended support of sub shape attribute, e.g. Compound1, Solid2,
      SubShape3 ('SubShape' is used to access child shape of a compound)

    * makeWires(), new API to sort and return wires given a list of edges.

    * transformed/translated/rotated/scaled(), return a new shape with
      some transformation.

    * findPlane(), find the plane of a planar shape

    * isCoplanar(), check if two shape are coplanar

src/Mod/Part/App/FeatureCompound.cpp

@@ -72,12 +72,10 @@ App::DocumentObjectExecReturn *Compound::execute(void)
 
         const std::vector<DocumentObject*>& links = Links.getValues();
         for (std::vector<DocumentObject*>::const_iterator it = links.begin(); it != links.end(); ++it) {
-            if (*it && (*it)->getTypeId().isDerivedFrom(Part::Feature::getClassTypeId())) {
-                Part::Feature* fea = static_cast<Part::Feature*>(*it);
-
-                auto pos = tempLinks.insert(fea);
+            if (*it) {
+                auto pos = tempLinks.insert(*it);
                 if (pos.second) {
-                    const TopoDS_Shape& sh = fea->Shape.getValue();
+                    const TopoDS_Shape& sh = Feature::getShape(*it);
                     if (!sh.IsNull()) {
                         builder.Add(comp, sh);
                         TopTools_IndexedMapOfShape faceMap;
@@ -108,3 +106,15 @@ App::DocumentObjectExecReturn *Compound::execute(void)
     }
 }
 
+////////////////////////////////////////////////////////////////////////
+
+PROPERTY_SOURCE(Part::Compound2, Part::Compound)
+
+Compound2::Compound2() {
+    Shape.setStatus(App::Property::Transient,true);
+}
+
+void Compound2::onDocumentRestored() {
+    auto res = execute();
+    delete res;
+}