Garbage system

When a user is deleting its account, all its personal information (login, password, email etc...) are deleted while its contributions (elements, releases, links etc...) can be saved. In this case, a special flag is set in the database for this account and a privileged user can choose to either save the contributions or dismiss them. One both cases, the user is definitely removed. If the data are saved, they are associated to the account with id garbageUserId (defined in the database configuration).