add assembly to gcompose, not working yet

src/Core/Object.h

@@ -52,6 +52,7 @@ class polymorphic_oarchive;
 namespace uLib {
 
 class PropertyBase;
+class ObjectsContext;
 
 class Version {
 public:
@@ -101,6 +102,9 @@ public:
   // FIXX !!!
   virtual void DeepCopy(const Object &copy);
 
+  /** @brief Returns a nested context for children objects, if any. */
+  virtual ObjectsContext* GetChildren() { return nullptr; }
+
   ////////////////////////////////////////////////////////////////////////////
   // SERIALIZATION //