LP1528301 Add SIP Support for BF field on type 10 checkin responses

LP1528301 Add SIP Support for BF field on type 10 checkin responses

This little patch will append the BF field in the SIP response during
checkin when the item is for another hold. Some self check software vendors
(ahem Bibliotheca) implement the hold phone number for the next patron this way.
You will need this patch as well as the code change to the SIPServer repo
LP1528301_Add_SIP_Support_for_BF_field_on_type_10_checkin_responses

Signed-off-by: blake <blake@mobiusconsortium.org>
Signed-off-by: Martha Driscoll <driscoll@noblenet.org>
Signed-off-by: Jason Boyer <jboyer@equinoxinitiative.org>