To enhance support of WebDAV access on Documents, the content_type and filename
properties needs to be set up with ERP5 API.

ERP5 API is less and less closer to OFS.Image API

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@41661 20353a03-c40f-0410-a6d1-a30d3c3de9de