Refactor tagging and add library scanning

- Replace `Tag` class with utility helpers for hashing and file type parsing
- Change `Track.artwork` from `std::string` to `TagLib::VariantMap`
- Add `importArtwork`, rename `importFolder` to `scanFolder`
- Add `scanLibrary`, `updateLibrary`, `editMetadata`, and `seek` methods to `Player` hierarchy
- Remove obsolete `Tag.h`/`Tag.cpp` files

include/PlayerLocal.h

@@ -1,17 +1,33 @@
 #pragma once
 
 #include "Player.h"
+#include "Database.h"
+
+using db = Database;
 
 class PlayerLocal : public Player {
   public:
+    // Library Controls
+    void loadFile ( Track track ) override;
+    void scanLibrary() override;
+    void updateLibrary() override;
+    void editMetadata() override;
 
+    // Transport Controls
+    void play() override;
+    void pause() override;
+    void stop() override;
     void next() override;
     void previous() override;
+    void seek() override;
     ma_uint64 getPlayheadPosition () override;
-    void loadFile ( Track track ) override;
+
+    // Queue
     void addToQueue( Track& track );
     void playQueue();
 
   private:
       unsigned int currentTrack_;
+      db db_;
+      std::string musicFolder_ = "data/";
 };