Bug 17932: Unit tests

Bug 17932: Unit tests

This patch adds unit tests for the Koha::Object::TO_JSON function.
It tests on top of Koha::Patron as Koha::Object needs to be
instantiated.

To test:
- Apply the patch
- Run:
  $ prove -v t/db_dependent/Koha/Object.t
=> SUCCESS: New tests for TO_JSON are run and return green.
- Sign off :-D

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>