Direct Debits; added minimum threshold for Other Direct Debit transactions

There is a new Minimum threshold for Direct Debiting other (ie non-Payment Due) amounts.

The minimum threshold is defined under the Account Type, Payments page.

This prevents small ad-hoc charges, eg a $5 letter fee, from being Direct Debited immediately. Instead the Direct Debit is held until it exceeds the minimum threshold or there is a payment due.