In order to safely import mail in ERP5, use the postUTF8MailMessage method from 
ERP5Type/patches/CMFMailIn.

getHeader was badly surcharged: it was not supposed to return a dict value.
It is forbidden to save dict attribute as a string.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@13523 20353a03-c40f-0410-a6d1-a30d3c3de9de