[FEM] add framework to scale result mesh values

- it seems that we will need to scale result values (probably for the Elmer Eigen solver)
  This PR adds the framework to do this. It is meant for Elmer but designed versatile.

src/Mod/Fem/Gui/ViewProviderFemPostPipelinePyImp.cpp

@@ -0,0 +1,64 @@
+/***************************************************************************
+ *   Copyright (c) 2022 Uwe Stöhr <uwestoehr@lyx.org>                      *
+ *                                                                         *
+ *   This file is part of the FreeCAD CAx development system.              *
+ *                                                                         *
+ *   This library is free software; you can redistribute it and/or         *
+ *   modify it under the terms of the GNU Library General Public           *
+ *   License as published by the Free Software Foundation; either          *
+ *   version 2 of the License, or (at your option) any later version.      *
+ *                                                                         *
+ *   This library  is distributed in the hope that it will be useful,      *
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+ *   GNU Library General Public License for more details.                  *
+ *                                                                         *
+ *   You should have received a copy of the GNU Library General Public     *
+ *   License along with this library; see the file COPYING.LIB. If not,    *
+ *   write to the Free Software Foundation, Inc., 59 Temple Place,         *
+ *   Suite 330, Boston, MA  02111-1307, USA                                *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "PreCompiled.h"
+
+#include <Base/VectorPy.h>
+#include <Base/GeometryPyCXX.h>
+
+#include "ViewProviderFemPostPipeline.h"
+
+// inclusion of the generated files (generated out of ViewProviderFemPostPipelinePy.xml)
+#include "ViewProviderFemPostPipelinePy.h"
+#include "ViewProviderFemPostPipelinePy.cpp"
+
+
+using namespace FemGui;
+
+// returns a string which represents the object e.g. when printed in python
+std::string ViewProviderFemPostPipelinePy::representation(void) const
+{
+    return std::string("<ViewProviderFemPostPipeline object>");
+}
+
+PyObject *ViewProviderFemPostPipelinePy::transformField(PyObject *args)
+{
+    char *FieldName;
+    double FieldFactor;
+
+    if (!PyArg_ParseTuple(args, "sd", &FieldName, &FieldFactor))
+        return nullptr;
+
+    this->getViewProviderFemPostPipelinePtr()->transformField(FieldName, FieldFactor);
+
+    Py_Return;
+}
+
+PyObject *ViewProviderFemPostPipelinePy::getCustomAttributes(const char * /*attr*/) const
+{
+    return nullptr;
+}
+
+int ViewProviderFemPostPipelinePy::setCustomAttributes(const char * /*attr*/, PyObject * /*obj*/)
+{
+    return 0;
+}