Bug 17669: [QA Follow-up] More consistency in return values of delete

Bug 17669: [QA Follow-up] More consistency in return values of delete

See Bugzilla comment36 (QA request).

Koha::UploadedFile->delete
Returns 1, 0E0 or -1 (unknown).

Koha::UploadedFiles->delete and delete_temporary
Returns number of deleted records, 0E0 or -1.

POD lines are corrected accordingly. Unit tests adjusted too.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Added a note that Koha::Object->delete itself is not completely consistent
with Koha::Objects->delete (DBIx). The singular may return 1 when it
gets 0E0 from DBIx, while the plural one may return 0E0. But should be
handled somewhere else.

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