Length instances are stored independantly in the ZODB, and as this property is
somehow often changed, it's better to have only a Length modified, not a
SQLCatalog. Also, without this, the history tab from the ZMI of the SQLCatalog
is unusable.



git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@13595 20353a03-c40f-0410-a6d1-a30d3c3de9de