Bug 6938 - replace two subscription fields that were incorrectly removed

Bug 6938 - replace two subscription fields that were incorrectly removed

The "Note for OPAC" and "Note for staff" fields in subscriptions were
removed, but they are their own fields in the database and display in
other places too. This patch puts them back so that they can once again
be edited.

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
(cherry picked from commit 2f11d527a0749e86350d62055f289aaee9435848)

Signed-off-by: Chris Nighswonger <chris.nighswonger@gmail.com>