USability issues fixed:
More ways to activate drop target: <a href="http://reviews.holehan.org/KGet/DropTarget#toc4">http://reviews.holehan.org/KGet/DropTarget#toc4</a>;
Popup for duplicate downloads: <a href="http://reviews.holehan.org/KGet/DropTarget#toc8">http://reviews.holehan.org/KGet/DropTarget#toc8</a>;
Error message when delete the main group: <a href="http://reviews.holehan.org/KGet/Settings#toc2">http://reviews.holehan.org/KGet/Settings#toc2</a>;