Add a user selectable tax_code_id to account_bank_statement_reconcile_line.

The Problem: Write-off entries are used as an adjustment for differences between the payment and the invoices to reconcile due to extra extraordinary losses, discounts etc. In a lot of countries these adjustments entail adjustments to taxes as well, but Open ERP treats taxes separately from the general accounts in "tax codes" and doesn't allow specifying them during the bank reconciliation process.

The Solution: Add a user selectable tax_code_id to account_bank_statement_reconcile_line.