Add Color record struct, small refactor, create a DaggerFramework.SceneGraph namespace.

Source/SceneGraph/Entities/Entity.cs

@@ -0,0 +1,27 @@
+using DaggerFramework.Audio;
+
+namespace DaggerFramework.SceneGraph
+{
+    public class Entity
+    {
+        public EntityLayer Layer { get; set; }
+        public InputHandler Input => Layer.Scene.Input;
+        public AudioBackend Audio => Layer.Scene.Audio;
+        public int Id { get; set; }
+
+        public void Start() => OnStart();
+        public void Update(double dt) => OnUpdate(dt);
+        public void ReceiveInput(InputHandler input) => OnInput(input);
+
+        protected virtual void OnStart() { }
+        protected virtual void OnDestroy() { }
+        protected virtual void OnUpdate(double dt) { }
+        protected virtual void OnInput(InputHandler input) { }
+
+        public void Destroy()
+        {
+            OnDestroy();
+            Layer?.DestroyEntity(Id);
+        }
+    }
+}