Bug 18124: Restrict CSRF token to user's session

Bug 18124: Restrict CSRF token to user's session

Currently the CSRF token generated is based on the borrowernumber, and
is valid across user's session.
We need to restrict the CSRF token to the current session.

With this patch the CSRF token is generated concatenating the id
(borrowernumber) and the CGISESSID cookie.

Test plan:
Run t/Token.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Mason James <mtj@kohaaloha.com>