#2 New Sample and Add Resolution : test the name

[Thomas Cambau]

when adding a new sample (or a new resolution), we should test if the name already exists in existing samples (resolutions).
This to avoid problems when deleting a sample (deleting its files may also delete a similar name's sample)

Quand addsample ou addresolution, il faut tester si le nom existe déjà parmis les sample ou resolution existantes.
Pour éviter des problèmes lors de la supression d'un sample (si un sample porte le meme nom, ses fichiers vont être delete).