OPAL-Flavor in the .stat file
In order to display properly the beam envelope in ROGER, we need to distinguished between OPAL-T (dataset x - y) and OPAL-Cyc (dataset x-z).
In case of reading from .h5 file, the attribute OPAL-Flavor is used to load the proper dataset. The OPAL-Flavor should be stored also in the .stat file, so that the correct envelope can be displayed when the .stat file is loaded in ROGER.