Bug 8062 [SIGNED-OFF] Cart email broken for non english templates

Bug 8062 [SIGNED-OFF] Cart email broken for non english templates

Fix basket email sent from OPAC. The email body is now generated HTML
(to be translatable), and converted into TEXT before beeing sent by
email.

To test that it works in other language than English, you have to update
your language .po file:

  perl translate update de-DE

Then, translated strings coming from opac-sendbasket.tt, and install the
translation:

  perl translate install de-DE

New dependency: Template::Plugin::HtmlToText

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>