Bug 16757 - Add ability to pay fee by id for SIP2

Bug 16757 - Add ability to pay fee by id for SIP2

The SIP protocol allows for a Fee Paid message to specify a fee
identifier in the CG field. While this field is read and passed to
C4::SIP::ILS::pay_fee, it is not passed along to
C4::SIP::ILS::Transaction::FeePayment::pay and is thus not used. We
should enable this functionality in Koha now that accountlines each have
a unique identifier that can be passed along to the payment requestor
via the AV field line items added by bug 14512.

Test Plan:
1) Create a fee in Koha
2) Ensure your SIP2 server is running and configured correctly
3) Send a 37 Fee Paid message to Koha's SIP server with the
   accountlines_id for that fee in the CG fee identifier field,
   along with the other required fields.
4) Note that specific fee was paid in Koha

Signed-off-by: Rhonda Kuiper <kuiper@roundrocktexas.gov>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>