Bug 17755: Introduce Koha::Object::Limit::Library

Bug 17755: Introduce Koha::Object::Limit::Library

This patch introduces a new class for extending Koha::Object using
multiple inheritance. It cannot be used standalone, it needs to be
used in Koha::Object implementations like this:

use base qw( Koha::Object Koha::Object::Limit::Library );

Its goal is to provide a single way and place to deal with this common
pattern in Koha's codebase.

As it happened with Koha::Object, that needed to be tested in a real object
class, this work was done on top of Koha::Patron::Attribute::Type implementation
and it is fully covered by the tests that are introduced for it.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>