FEM: ccx input writer, splitted, improve node sets for displacement constraint
FEM: ccx input writer, splitted, improve node sets for displacement constraint

Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master