Bug 37510: Make Koha::Object->delete throw Koha::Exception

Bug 37510: Make Koha::Object->delete throw Koha::Exception

This patch makes Koha::Object->delete wrap DBIC exceptions on FK
constraints and throw a Koha::Exception::Object::FKConstraint exception
instead. This will allow us better handling it from the callers.

To test:
1. Apply the unit tests patch
2. Run:
   $ ktd --shell
  k$ prove t/db_dependent/Koha/Object.t
=> FAIL: A DBIC exception is thrown instead, tests fail
3. Apply this patch
4. Repeat 2
=> SUCCESS: Tests pass!
5. Sign off :-D

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Pedro Amorim <pedro.amorim@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>