Python adjustments (#7809)

* #7797 Well Targets: Add scripting capability
* #7794 Python : Do not update childField or childFieldArray
* #7797: Python - Add scripting to well path collection
- Extend the pdmobject.py with method add_object()
- allow objects to be created from Python in well path collections
- add well targets to modelled well path

* #7795 Python : Make sure referenced generated classes are defined
* #7810 StimPlanModel: clean-up python generation
* Python : Always use empty string as default value for ptrFieldValue
It can happen that a ptrField is assigned to a pointer on object construction. (FaciesProperties) Make sure that constructor always assigns an empty string.

Co-authored-by: magnesj <magnesj@users.noreply.github.com>
Co-authored-by: Kristian Bendiksen <kristian.bendiksen@gmail.com>

Fwk/AppFwk/cafProjectDataModel/cafPdmCore/cafPdmObjectHandle.h

@@ -104,6 +104,8 @@ public:
     virtual void onChildDeleted( PdmChildArrayFieldHandle*           childArray,
                                  std::vector<caf::PdmObjectHandle*>& referringObjects );
 
+    virtual void onChildAdded( caf::PdmFieldHandle* containerForNewObject ){};
+
 protected:
     void addField( PdmFieldHandle* field, const QString& keyword );