[IMP] [FIX] email_template: do not sanitize the template content.

Indeed its content may contain invalid html that could be stripped by the
sanitizer. The content generated based on the template will be sanitized
when stored in the mail_mail or mail_message body field, thus after
rendering.

bzr revid: tde@openerp.com-20140227144228-d275lxz6ryarkg4t