reset playlist to first track on stop

LenaPi/controllers/MusicPlayer.h

@@ -62,9 +62,18 @@ public slots:
     void playPrevious();
 
 private:
-    void reset();
-    void clearMediaList();
+    /**
+     * @brief Resets playlist to first track if playlist exists and is non-empty
+     */
+    void resetPlaylistToFirstTrack();
+    void clearPlaylist();
     void readMedia(const QString& path);
+    /**
+     * @brief Transforms time in milliseconds into a string
+     * @param time Time in ms
+     * @return
+     * @todo use QDateTime
+     */
     QString timeToString(int time);
 
     int mCurrentMediaItemLength = 0;