Update of the model
I updated the app model by:
- removing all uncessary fields in the user table (that now resides in
the django auth_user table)
- update the other models by doing the same
- reorder the fields to have something more logical to read
- update the docstring to fit the updated description
Signed-off-by:
Matthieu Berjon <matthieu.berjon@inria.fr>