Bug 14187: branchtransfer needs a primary key (id) for DBIx and common sense.

Bug 14187: branchtransfer needs a primary key (id) for DBIx and common sense.

* C4/Circulation.pm (GetTransfers, GetTransfersFromTo): Also return
  branchtransfer_id in return columns.
* installer/data/mysql/atomicupdate/14187.perl: New file.
* installer/data/mysql/kohastructure.sql: Modify branchtransfers structure.
* t/db_dependent/Circulation/transfers.t: Update tests to expect
  branchtransfer_id.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Test plan successful on all steps.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Amended patch: Remove Schema changes from this patch
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>