Avoid going to JNI-land more than once per TorrentStatus object

`TorrentHandle.getStatus()` creates a `TorrentStatus` object every 500ms for every torrent we're currently downloading, these objects then are queried and each time we have to go to JNI land to obtain what is supposed to be (according to the documentation) a snapshot of the Torrent State.

In this proposal patch, I keep the TorrentStatus object for another 500ms and I keep the TorrentStatus properties in Java land.