Added additional documentation which makes clear that the added class is...

Added additional documentation which makes clear that the added class is necessary to create the sharedPlanePtr in Python.

core/include/SharedPlanePtr.h

@@ -40,7 +40,7 @@ namespace genfit {
     typedef std::shared_ptr< genfit::DetPlane > SharedPlanePtr;
 
     /**
-     * Class allowing to create a SharedPlanePtr from a DetPlane.
+     * Class allowing to create a SharedPlanePtr from a DetPlane from Python.
      */
     class SharedPlanePtrCreator {
     public: