Comment 1 for bug 1380709

Code to implement the above pushed to:

http://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/berick/lp1380709-fund-debit-invoice-links

Confirmed it resolves the problem described above.

Since this tracks (and thus requires) new data, it will only effect invoices created or modified after the code is applied. All other invoices / debits will behave as before.