Deleted some files that won't be needed in the package. I kept them in local if needed, but they're in git anyway. I added the constants on the ELBO on the PLN model to get a stop criteria.
I also modified the stop criterion of the IMPS_model : We add 1 to the criterion if the log likelihood had not be improved for nb_trigger epoch. We stop when the criterion reahces the parameter nb_plateau.
I also did some minor modifications in the utils.


Former-commit-id: 1f224df8314fa4a7c9818a21874afac17cfefbed