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

Source/SceneGraph/Entities/Sprite2d.cs

@@ -0,0 +1,25 @@
+using System.Drawing;
+
+using DaggerFramework.Rendering;
+
+namespace DaggerFramework.SceneGraph
+{
+    public class Sprite2d : Drawable2d
+    {
+        public Texture2d Texture { get => _texture; set => _texture = value; }
+
+        protected override void OnStart()
+        {
+            var renderer = Layer.Scene.Renderer;
+            _texId = renderer.LoadTexture(_texture);
+        }
+
+        public override void OnDraw(Renderer renderer)
+        {
+            renderer.DrawTexture(_texId, Color.White);
+        }
+
+        private Texture2d _texture;
+        private int _texId;
+    }
+}