Changes

Tsk31 Adds the access control in the service UserService
Modifies the UserService to keep an access control by role. The service 
findStories, which is to get the stories of an author, is adapted to
take an access control by role and by the own user of the stories. The
name of this service has been changed by findStoriesByAuthor to support
a concordance with its action. In addition, the param is now the login
of the author to control the access in the down layers and prevent have
to control the access in the REST and JSF layers.