EDI invoice date; invoice paid quantity/amount

EDI invoice date; invoice paid quantity/amount

* capture the invoice date in EDIReader
* apply the invoice date to inbound invoices when available instead of
  defaulting to 'now'
* apply the quantity/amount billed to the quantity/amount paid to reduce
  staff data entry needs

Signed-off-by: Bill Erickson <berick@esilibrary.com>
Signed-off-by: Lebbeous Fogle-Weekley <lebbeous@esilibrary.com>