Load magnet metadata inside AddNewTorrentDialog
Add progress indicator for metadata retrieval
Merge pull request #818 from Gelmir/metadata2

Load magnet metadata inside AddNewTorrentDialog
Don't show the progress bar in AddNewTorrent dialog when not necessary.
Always override AddTorrentsInPause setting when downloading in the background.
Simplify checks.
Simplify busy wait.
Fix typo in comment.
Merge trackers when torrent already exists instead of showing an AddNewTorrent dialog.
Fix ETA calculation when some files are downloaded and marked afterwards as 'do not download'.
Mark strings as translatable. Closes #893.
Run lupdate.
Display a message when a link to a search plugin is invalid. Closes #892.
Run lupdate.
Visually show that the private flag are respected and that PEX/DHT/LSD is disabled. Closes #880.
Fix string typo and rerun lupdate.