Changes

tsk23, tsk25 Adds role atribute to User and adds RoleCallers
Added the role attribute as a String on the user, initialized with
"user" value by default in constructor. Updated datasets including role. 
Added security calling the role of the currentUser by access control. 
Updated UserEJBTest and EventEJBTest in order to get the login of the
RoleCallers
Settled as user by default