API renames, change ref renderer to in renderer in IDrawable, make Layer implement IDrawable.

Source/EntityLayer.cs

@@ -45,11 +45,11 @@ namespace DaggerFramework
             }
         }
 
-        protected override void OnDraw(ref Renderer renderer)
+        protected override void OnDraw(in Renderer renderer)
         {
             foreach (IDrawable drawable in _entities)
             {
-                drawable.Draw(ref renderer);
+                drawable.Draw(in renderer);
             }
         }