Changes

tsk 1 Adds user attributes for the account activation process
Adds 3 attributes: isActivated - indicates the activation status. 
registerDate - indicates the date of the account creation. 
activationUUID - this is a universal unique ID that allows to identify
an user to activate his account.
The addition of this attributed forced to modify the datasets of the EJB
layer and the IsEqualToUser class. For the activation process was
necesary to add 2 more methods to the UserService: getByUUID() - allows
to find in the database the user that is trying to activate his account. 
activateUser() - allows to modify the user account status to
"activated".