Add Database and refactor player/playback

Add Database class with SQLite fetch/fetchAlbum methods. Refactor
PlaybackEngine (data callback, seek, getPosition, decoder lifecycle)
and Player API (PlaybackEngine member, queue handling, PlayerLocal).
Update Metadata::Track fields to include artist/title/album/trackNr/length.

include/PlayerEngine.h

@@ -11,10 +11,13 @@ class PlayerEngine {
         unsigned int sampleRate_;
         unsigned int channels_ = 2;
         ma_format format_ = ma_format_unknown;
+        ma_context context_;
+
 
     public:
         PlayerEngine();
         PlayerEngine( unsigned int sampleRate, unsigned int channels, ma_format format );
+        ~PlayerEngine();
         ma_device getDevice() const;
         unsigned int getChannels() const;
         unsigned int getSampleRate() const;
@@ -24,4 +27,10 @@ class PlayerEngine {
         void setSampleRate( unsigned int sampleRate );
         void setChannels( unsigned int channels );
         void setFormat( ma_format format );
+
+        ma_device_data_proc data_callback();
+        void configureDevice( ma_context& context );
+        void initDevice ();
+        void initEngine();
+
 };