session loading: fix the default format of files
When the format is not present, we use the extension of the file to generate it. This fixes a problem that occured in Python files when old sessions were kept, the file would become not parsable.
Prochaines maintenances programmées: mardi 02/04, lundi 06/05, lundi 03/06
Pour plus d'informations: https://doc-si.inria.fr/display/SU/Gitlab
When the format is not present, we use the extension of the file to generate it. This fixes a problem that occured in Python files when old sessions were kept, the file would become not parsable.