Bug 9348 - Format dates in HOLD notices consistently

Right now notices for holds awaiting pickup read something like this:

You have a hold available for pickup as of 2011-02-12.
This hold will expire if it is not picked up before: 02/22/2011.
If you no longer need this item or have any questions please contact us

Both dates should be formatting based on the dateformat system preference.

Test Plan:
1) Apply patch
2) Set the HOLD notice to the following:
    <<reserves.waitingdate>> / <<reserves.expirationdate>>
3) Place a hold for a patron
4) Enable the HOLD notice via email for that patron ( requires EnhancedMessaging )
5) Check the item in
6) Go to the borrower's Notices tab, check the body of the new HOLD notice,
   it should have two dates separated by a '/' in the format set by the dateformat
   system preference.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>

Patch works as advertised according to the test plan.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Tested also with the HOLD_PRINT notice.
Merge branch 'bug_9348' into 3.12-master