FEM: python base constraint, add Object attribute

src/Mod/Fem/femobjects/FemConstraint.py

@@ -32,6 +32,7 @@ class Proxy(object):
     BaseType = "Fem::ConstraintPython"
 
     def __init__(self, obj):
+        self.Object = obj  # keep a ref to the DocObj for nonGui usage
         obj.Proxy = self  # link between App::DocumentObject to this object
 
 ##  @}