First attempt at bringing the AddNewTorrentDialog to the front.

This should close:  #166 #327 #443 #698

On platforms other than Windows this should work with the patch.
On Windows we need some hack where our dialog becomes momentarily ALWAYSONTOP and immediately loses that attribute. It works but in eg firefox which displays an animation when a download is complete(.torrent is downloaded) it hides the dialog again. At least now with activateWindow() the taskbar entry is flashing.

Any ideas?