credit on created line (and adjust cents on the last line if needed, and if the 
difference is not too big, not to hide error in the configuration).
Enable AccountingTransaction_roundDebitCredit to be called on generated invoices.

This should fix testAccountingRules



git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@13897 20353a03-c40f-0410-a6d1-a30d3c3de9de