Join improvements (added summary page to confirm the operation)

classes/UserHandler.php

classes/datalayer/mysql/MySQLUserDAO.php

classes/exceptions/ServerErrorException.php

classes/login/LoginHandler.php

classes/model/SessionData.php

include/front-controller.php

include/identities.php

include/user-data.php

index.php

sql/setup-database.sql

views/account-management.php

views/confirm-join.php

views/error.php

views/services-list.php

views/tou-check.php