Now, all constraint are required field too. This is because off the so horrible displaying of constraint errors. Required fields are very nice diplayed, and it's very easy to understand what is required and why it's not possible to save the document.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@22799 20353a03-c40f-0410-a6d1-a30d3c3de9de