Bug 14512 - Add support for AV field to Koha's SIP2 Server

 Bug 14512 - Add support for AV field to Koha's SIP2 Server

Koha's SIP2 server should have support for the AV field ( field items ).
The biggest problem with this field is that its' contents are not really
defined in SIP2 protocol specification. All it says is "this field
should be sent for each fine item". Due to this, I think the contents of
the field need to be configurable at the login level, so that the
contents can be defined based on the SIP2 devices requirements for the
AV field.

Test Plan:
1) Apply this patch
2) Find a patron with outstanding fines
3) Run a patron information request using misc/sip_cli_emulator.pl using the new -s option with the value "   Y      "
4) Note there is an AV field for each fee containing the description and amount
5) Edit your sip config, add an av_field_template parameter to the login you are using such as
    av_field_template="TEST [% accountline.description %] [% accountline.amountoutstanding | format('%.2f') %]"
6) Restart your SIP server
7) Repeat the patron information request
8) Note your custom AV field is being used!

Signed-off-by: Chris Davis <cgdavis@uintah.utah.gov>
Signed-off-by: Jesse Weaver <jweaver@bywatersolutions.com>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>