The set of filter groups available to the TPAC are those defined at the
search org unit and its ancestors. If multiple filters have the same
code name, the filter owned closest to the context org unit is used.
This allows for global filters with local overrides.
Signed-off-by: Bill Erickson <berick@esilibrary.com> Signed-off-by: Mike Rylander <mrylander@gmail.com>