Internal referene is now used, which is ok for internal bank accounts (their reference property contains  the internal reference) but not ok for other bank accounts. String index contains the internal reference in all cases.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@14427 20353a03-c40f-0410-a6d1-a30d3c3de9de