New context with albums and lyrics +++ much more

* Added new lyrics provider with lyrics from AudD and API Seeds
* New improved context widget with albums and lyrics
* Fixed playing and context widget getting stuck in play mode when there was an error
* Changed icons for artists in collection, tidal and cover manager
* Removed "search" icon from "Search automatically" checkbox (right click) that looked ugly
* Removed some unused widgets from the src/widgets directory
* Fixed initial size of window and side panel
* Fixed saving window size correctly

src/lyrics/lyricsprovider.h

@@ -0,0 +1,52 @@
+/*
+ * Strawberry Music Player
+ * Copyright 2018, Jonas Kvinge <jonas@jkvinge.net>
+ *
+ * Strawberry is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Strawberry is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Strawberry.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef LYRICSPROVIDER_H
+#define LYRICSPROVIDER_H
+
+#include "config.h"
+
+#include <stdbool.h>
+
+#include <QObject>
+#include <QList>
+#include <QString>
+
+struct LyricsSearchResult;
+
+class LyricsProvider : public QObject {
+  Q_OBJECT
+
+public:
+  explicit LyricsProvider(const QString &name, QObject *parent);
+
+  QString name() const { return name_; }
+
+  virtual bool StartSearch(const QString &artist, const QString &album, const QString &title, quint64 id) = 0;
+  virtual void CancelSearch(quint64 id) {}
+
+signals:
+  void SearchFinished(quint64 id, const QList<LyricsSearchResult>& results);
+
+private:
+  QString name_;
+
+};
+
+#endif // LYRICSPROVIDER_H