Conversion Utilities; added new function to update Next Payment Date for Closed Fixed Term Loans

A new function has been added to finConversionUtilities to force a Closed Loan Account's next payment date to 30/12/3000 - so that if it is re-opened Payments aren't re-processed.

The new function is AccountUpdateClosedFixedTermLoanPaymentDate.

The standard conversion utility has been updated to version 4.21 dated 1/12/2014/