User wants to be able to run an outstanding po detail report for a particular period and have it accurately reflect the encumbrance amount as of that period.

We need to add a getter to retrieve the encumbered amount as of the current period.  Let's call it CurrentPeriodRemainingEncumbrance.

This report will be very similar to the existing PO Detail report, it will just use this new method.  The report should be called Outstanding Purchase Order Report