Improve strip torrent root folder

Fix issue when you rename the "root item" in the "Add New Torrent" dialog
and uncheck "Create subfolder", it will create the subfolder with the
renamed name.
Fix PropertiesWidget first folder is expanded after app restart.
Strip root folder if torrent was added via magnet link.
Fix crash when you get name of torrent without metadata.

src/base/bittorrent/torrenthandle.h

@@ -98,7 +98,7 @@ namespace BitTorrent
         bool sequential;
         bool hasSeedStatus;
         bool skipChecking;
-        bool createSubfolder;
+        bool hasRootFolder;
         TriStateBool addForced;
         TriStateBool addPaused;
         // for new torrents
@@ -236,6 +236,8 @@ namespace BitTorrent
         bool belongsToCategory(const QString &category) const;
         bool setCategory(const QString &category);
 
+        bool hasRootFolder() const;
+
         int filesCount() const;
         int piecesCount() const;
         int piecesHave() const;
@@ -396,7 +398,7 @@ namespace BitTorrent
         Session *const m_session;
         libtorrent::torrent_handle m_nativeHandle;
         libtorrent::torrent_status m_nativeStatus;
-        TorrentState  m_state;
+        TorrentState m_state;
         TorrentInfo m_torrentInfo;
         SpeedMonitor m_speedMonitor;
 
@@ -422,6 +424,7 @@ namespace BitTorrent
         qreal m_ratioLimit;
         bool m_tempPathDisabled;
         bool m_hasMissingFiles;
+        bool m_hasRootFolder;
 
         bool m_pauseAfterRecheck;
         bool m_needSaveResumeData;