[MOD] Way of confection of apo in multicurrency mode

With this change and in multicurrency mode on "Journal != company_currency" the following changes occur in functional level:

1. Full reconcile of line suggests the amount_unreconciled_currency of the invoice
2. Changes in the amount_unreconciled_currency triggers computation of field amount based on the APO currency rate
3. Changes in the amount does not trigger recomputation of the field amount_unreconciled_currency