Bug 26635: AV expansion should ackowledge $params->{public}

This patch simplifies the original implementation so it is more
readable, removing extra loops and methods and just dealing with the
coded values inline on the existing loops.

It also adds non-public attributes removal from the original list, to
address the changes introduced by bug 28948.

To test:
1. Apply this patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/Object.t \
           t/db_dependent/Koha/REST/Plugin/Objects.t
=> SUCCESS: Tests pass!
3. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>