Correct problems with editing shopping cart

Most of these changes improve debugging output for the shopping
cart. The primary change of substance is PaymentSystemImpl line 309,
where we needed to check the country for null so the update
transaction can complete.
Merge remote-tracking branch 'origin/trello-143-editShopping' into dryad-master

Conflicts:
	dspace/modules/payment-system/payment-api/src/main/java/org/dspace/paymentsystem/PaymentSystemImpl.java