Bug 17501: Introduce Koha::Object[s] classes for UploadedFile(s)

Bug 17501: Introduce Koha::Object[s] classes for UploadedFile(s)

In the next set of patches we will start using these new classes in
Koha::Upload, and scripts using it.
This is just the starting point of that migration.

Test plan:
[1] Run t/db_dependent/Upload.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>