General Ledger Export; added "BankExportPk" to "Universal" export type

When exporting Bank Transactions in the General Ledger Export, Bank Transactions are either sent through individually or grouped by Lodgement/ Bank Export (eg as in a Direct Credit or Debit batch). This matches the Bank Statement detail in the Cash Book.

An enhancement has been made to the "Universal" export type to include the "BankExportPk" where Bank Transactions have been grouped.

So, a Bank Transaction line will either include "Pk" or "BankExportPk", depending on whether or not it was grouped.