Deposit Interest; update code for checking if valid to pay Interest via Direct Credit/ Cheque

The program code used to determine if a Deposit Interest Payout via Direct Credit/ Cheque can be made has been updated to make it easier to understand.

NOTE: There is no change to the actual rules - Interest Payouts by Direct Credit or Cheque will only occur if they could be processed on the date by the Bank - i.e., you cannot backdate an Interest Payout. But, remember the Interest Payout transaction is dated the same day as the Interest transaction, and therefore would normally be actually paid the day after.

In addition, there is an Account Type option "Roll Interest Payout Date forward if it falls on a non-Business Day?" that would normally be checked.