Bug 28490: Bring back accidentally deleted relationship columns

Bug 28490: Bring back accidentally deleted relationship columns

These were in active use before and were accidentally deleted in Bug
26995. This restores those deleted relationship columns.

To test:
 1) verify the borrower_modifications, borrowers,
    deletedborrowers contain the column exactly like it was before after
    applying these patches by comparing to the old kohastructure.sql
    version

Signed-off-by: Petro Vashchuk <stalkernoid@gmail.com>
Signed-off-by: Emmi Takkinen <emmi.takkinen@koha-suomi.fi>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>