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.

src/PlayerLocal.cpp

@@ -0,0 +1,37 @@
+#include "../include/PlayerLocal.h"
+#include "../include/Player.h"
+
+void Player::play () { PE_.startPlayback(); }
+void Player::stop () { PE_.stopPlayback(); }
+void PlayerLocal::next() {
+    unsigned int nextTrack = ++currentTrack_;
+    PE_.uninitDecoder();
+    loadFile( queue_.at( ++currentTrack_));
+    PE_.startPlayback();
+}
+void PlayerLocal::previous() {
+    unsigned int previousTrack = --currentTrack_;
+    PE_.uninitDecoder();
+    loadFile( queue_.at( --currentTrack_));
+    PE_.startPlayback();
+
+}
+
+ma_uint64 Player::getPlayheadPosition () { return PE_.getPosition(); };
+
+void PlayerLocal::loadFile ( Track track ) {
+    const char *fp = track.filePath;
+    PE_.initDecoder ( fp );
+}
+
+void PlayerLocal::addToQueue( Track& track ) {
+    queue_.push_back( track );
+}
+
+void::PlayerLocal::playQueue() {
+    for ( Track track : queue_ ) {
+        loadFile( track );
+        play();
+        ++currentTrack_;
+    }
+}