Bug 8621: Alternative template for cart email

Bug 8621: Alternative template for cart email

- uses less list elements, in favour of paragraphs and line breaks
- reimplements a link to the opac for each record

Note: In order for the URLs to be correct this needs to be tested
together with the patch for bug 8626.

To test:
- Add several records to the cart, add items with and without items
- Send yourself the cart as email and check formatting
- Update po files for any language, translate the po file for OPAC
  and install language
- Send yourself the cart email again from the translated templates,
  check formatting

Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>