Bug 17189: Add the ability to define several memcached namespaces - Koha::Caches

Bug 17189: Add the ability to define several memcached namespaces - Koha::Caches

We need to define several namespaces for our cache system.
For instance sysprefs, koha conf (koha-conf.xml) and unit tests
should be defined in a separate namespace.
This will permit to
- launch the tests without interfering with other cache values
- and flush the sysprefs cache without flushing all other values

To do so, we need to store different Koha::Cache objects at a package
level. That's why this patch adds a new Koha::Caches module.

FIXME: There is an architecture problem here: the L1 cache should be
defined in Koha::Cache

Signed-off-by: Jacek Ablewicz <abl@biblos.pk.edu.pl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
https://bugs.koha-community.org/show_bug.cgi?id=11921

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>