Preparing bugfix branch for 1.6.x fixes, particularly issue #55.
Modified register() service to add the paymentId to the results object
that is passed back to the client upon successful registration.  This
allows the client to set the invoice number properly and avoids the
paypal bug in which invoices are not matched to payments.  Fixes issue
#55.
Modify register() service to use more precise selection of the proper
roster entry after one is created using a particular primary key.