Bug 26057: Add datecancelled, cancellation_reason fields

Bug 26057: Add datecancelled, cancellation_reason fields

This patch adds the datecancelled and cancellation_reason fields to the
branchtransfers table to record when and why transfers have been
cancelled.

To test
1/ Run the database update
2/ Check the database for the 'datecancelled' and 'cancellation_reason'
fields
3/ Signoff

Signed-off-by: Kathleen Milne <kathleen.milne@cne-siar.gov.uk>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@helsinki.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>