API-method "append" and duplicate check #284
When adding nzb-file if duplicate check puts it straight to history with status DUPE, COPY, etc. the API-method "append" returns "-1" as indication of an error.
One consequence of this is that the automation programs may try to send the same file again (and again).
It would be better to return the ID of item in the history instead of "-1". That will allow the other programs check the status of nzb and react properly.