Refactor metadata and internal data structures

Replace Metadata.h with Containers.h, introducing a HashTable
implementation with SIMD acceleration and specialized track tracking.
Cleanup PlayerEngine logic by merging it into the playback flow and
refactoring several internal API signatures.

include/Player.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../include/Metadata.h"
+#include "../include/Containers.h"
 #include "../include/PlaybackEngine.h"
 #include "../include/miniaudio.h"
 
@@ -8,7 +8,8 @@
 #include <string>
 #include <vector>
 
-using Queue = std::vector<Track>;
+using trackVec = std::vector<Track>;
+using ht = HashTable;
 
 class Player {
   public:
@@ -33,16 +34,16 @@ class Player {
     virtual std::string &getAlbum () const;
     virtual unsigned int getTrackNr () const;
 
-    // Player Queue
-    Queue getQueue () const;
-    Queue clearQueue ();
+    // Player trackVec
+    trackVec getQueue () const;
+    trackVec clearQueue ();
     void addToQueue ( Track &track );
-    Queue rempveFromQueue ( Track &track );
-    Queue shuffleQueue ();
+    trackVec rempveFromQueue ( Track &track );
+    trackVec shuffleQueue ();
 
   protected:
     PlaybackEngine PE_;
-    Queue queue_;
+    trackVec queue_;
 
   private:
     std::string artist_;
@@ -53,4 +54,9 @@ class Player {
 
     unsigned int samplerate_ = 48000;
     unsigned int channels_ = 2;
+
+    trackVec tracks;
+    ht songs;
+    ht artists;
+    ht albums;
 };