Bug 17501: Move getCategories and httpheaders from Upload.pm

Bug 17501: Move getCategories and httpheaders from Upload.pm

Class method getCategories has no strict binding to Upload.pm. While
Upload.pm is now restricted to the actual uploading process with CGI
hook, this routine fits better in the UploadedFile package.

Class method httpheaders can be moved as well for the same reason. Note
that it actually is an instance method. The parameter $name is dropped.

Test plan:
[1] Run t/db_dependent/Upload.t.
[2] Check the categories in the combo box of tools/upload.
[3] Check a download via tools/upload and opac-retrieve-file.

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>