Improve album cover searching and cover manager, use HttpStatusCodeAttribute and QSslError for services

- Improve album cover manager
- Change art_automatic and art_manual to QUrl
- Refresh collection album covers when new album covers are fetched
- Fix automatic album cover searching for local files outside of the collection
- Make all Json services check HttpStatusCodeAttribute
- Show detailed SSL errors for Subsonic, Tidal and Qobuz

src/context/contextview.h

@@ -131,9 +131,9 @@ class ContextView : public QWidget {
   void ActionShowAlbums();
   void ActionShowLyrics();
   void UpdateLyrics(const quint64 id, const QString &provider, const QString &lyrics);
-  void SearchCoverAutomatically();
+  void SearchCoverInProgress();
   void AutomaticCoverSearchDone();
-  void AlbumArtLoaded(const Song &song, const QString &uri, const QImage &image);
+  void AlbumCoverLoaded(const Song &song, const QUrl &cover_url, const QImage &image);
   void FadePreviousTrack(qreal value);
 
 };