Bug 24083: Required atomic updates & DB update

Bug 24083: Required atomic updates & DB update

This patch adds:

- An "UnseenRenewals" circulation syspref that enables/disables the
  functionality added in this bug

- Add unseen_renewals_allowed to circulation_rules

- A change to the issues & old_issues table schemas and corresponding
  database upgrades to add issues.unseen_renewals &
  old_issues.unseen_renewals

Signed-off-by: Sally Healey <sally.Healey@cheshirewestandchester.gov.uk>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>