FEM: get pressure faces ids, some better comments and very small code improvement

src/Mod/Fem/femsolver/calculix/writer.py

@@ -1157,6 +1157,9 @@ class FemInputWriterCcx(writerbase.FemInputWriter):
             rev = -1 if prs_obj.Reversed else 1
             f.write("*DLOAD\n")
             for ref_shape in femobj["PressureFaces"]:
+                # the loop is needed for compatibility reason
+                # in depretiated method get_pressure_obj_faces_depreciated
+                # the face ids where per ref_shape
                 f.write("** " + ref_shape[0] + "\n")
                 for face, fno in ref_shape[1]:
                     if fno > 0:  # solid mesh face