Bug 24321: Add Koha::Objects->attributes_from_api

Bug 24321: Add Koha::Objects->attributes_from_api

This patch makes the 'attributes_from_api' method from the singular
class available from the result set class.

To test:
1. Apply this patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/Objects.t
=> SUCCESS: Tests pass!
4. Sign off :-D
5. Yeah, I skipped 3 :-P

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>