Launchpad automatic translations update.
[FIX] mail_followers: avoid partners_to_notify parameter in _notify only if None, not if void.
[FIX] portal mail: Override of _search and check_access_rule of mail_message to add specific access rights of mail.message, to remove all no discussion message if uid is a portal user.
[IMP] mail_message for portal users: actually only comment without subtype are not shown (internal notes).
[FIX] portal: mail_message: override of _search and check_access_rule of mail_message in order to remove all internal notes if uid is not an employee.
[FIX] account_voucher: display the multi-currency options each time needed
[IMP] account_voucher, usability: reset the amount to 0 in the 'pay invoice wizard' if the currency is not the same than the invoice currency to avoid a common mistake
[IMP] account_voucher, usability: added currency_help_label to help at the understanding when using the payment rate fields