Fix transfer list architecture

Model returns string for DisplayRole.
Text alignment is set by Model (using TextAlignmentRole).
Delegate performs custom painting only where necessary
(i.e. for Progress bar).

src/gui/transferlistmodel.h

@@ -34,11 +34,11 @@
 #include <QColor>
 #include <QList>
 
+#include "base/bittorrent/torrenthandle.h"
+
 namespace BitTorrent
 {
     class InfoHash;
-    class TorrentHandle;
-    enum class TorrentState;
 }
 
 class TransferListModel : public QAbstractListModel
@@ -84,6 +84,12 @@ public:
         NB_COLUMNS
     };
 
+    enum DataRole
+    {
+        UnderlyingDataRole = Qt::UserRole,
+        AdditionalUnderlyingDataRole
+    };
+
     explicit TransferListModel(QObject *parent = nullptr);
 
     int rowCount(const QModelIndex &parent = {}) const override;
@@ -105,9 +111,12 @@ private slots:
     void handleTorrentsUpdated(const QVector<BitTorrent::TorrentHandle *> &torrents);
 
 private:
+    QString displayValue(const BitTorrent::TorrentHandle *torrent, int column) const;
+    QVariant internalValue(const BitTorrent::TorrentHandle *torrent, int column, bool alt = false) const;
+
     QList<BitTorrent::TorrentHandle *> m_torrentList;  // maps row number to torrent handle
     QHash<BitTorrent::TorrentHandle *, int> m_torrentMap;  // maps torrent handle to row number
-
+    const QHash<BitTorrent::TorrentState, QString> m_statusStrings;
     // row text colors
     QHash<BitTorrent::TorrentState, QColor> m_stateForegroundColors;
 };