[FIX] account: tax adjustment wizard fixed.

The former version of the tax adjustment wizard was copying the selected tax on both the credit and debit line of the created journal entry. Although it was fine for the belgian use case (since the report was taking only the sum.debit or sum.credit to gather data for grid 61/62), this was a stupid limitation as it was preventing to use that wizard to touch any grid using sum.balance (as both lines would be taken into account and cancelling each other).

To enhance/fix this, we introduce a fields.selection in the wizard to depict if the tax needs to be copied on the debit OR the credit line.

Inspired by ticket 1826242.