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/contextalbumsmodel.h

@@ -109,7 +109,7 @@ class ContextAlbumsModel : public SimpleTreeModel<CollectionItem> {
   void LazyPopulate(CollectionItem *item, bool signal);
 
  private slots:
-  void AlbumArtLoaded(quint64 id, const QImage &image);
+  void AlbumCoverLoaded(const quint64 id, const QUrl &cover_url, const QImage &image);
 
  private:
   QueryResult RunQuery(CollectionItem *parent);