LP#1346381: Allow copy location filters above branches

LP#1346381: Allow copy location filters above branches

The TPAC, inheriting functionality from the JSPAC, restricted the
copy locations one could filter on in the advanced search screen.
For installations that have many shared copy locations at the (stock-speak)
System level and just a few Branch level special locations, this is
sub-optimal.

This commit allows the display of System-and-above copy locations
for filtering, but excludes Branch-level locations in order to avoid
the heretofore protected-against location list explosion.

Signed-off-by: Mike Rylander <mrylander@gmail.com>