Perform migration of bt-specific Property Sheets from filesystem to
Arnaud Fontaine authored
ZODB (code previously commented by r42901 but at that time the
migration was not performed because of _perform_migration being set to
False and then enabled in r42902)



git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@42922 20353a03-c40f-0410-a6d1-a30d3c3de9de
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