Add a "staff_alert" column to config.standing_penalty, and ...

Add a "staff_alert" column to config.standing_penalty, and ...

... consult this when deciding whether to show the stop sign page in the
patron interface of the staff client, rather than explicitly checking
for the id of the ALERT_NOTE config.standing_penalty.

Now only show the standing penalty if the staff_alert value is true,
instead of unconditionally showing it for all penalties with a
block_list value.  This allows staff to configure blocking penalties
that do not alert.

Signed-off-by: Bill Erickson <berick@esilibrary.com>
Signed-off-by: Lebbeous Fogle-Weekley <lebbeous@esilibrary.com>