Process Interest Payouts; finAccountInterestPayout.CanCombine() Function added

The Payment Method indicates whether Payouts can be combined for a Client. Previously, the User Interface was responsible for enforcing this setting in the Process Direct Debits wizard. Due to the addition of the Process Interest Payouts HTML Widget, this has been moved to the Business Layer.

Therefore, finAccountInterestPayout.CanCombine() has been added, and the User Interface has been updated to refer to this Function. If the Interest Payout has been processed, or cannot be exported, this Function returns False. Otherwise, it will return the Payment Method setting "Combine Interest Payouts for the same 'Main' Client?"