Data bindings - Fixed some conversion issues

Data bindings - Started hooking up the UI

src/Artemis.Core/Events/LayerPropertyGroupUpdatingEventArgs.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace Artemis.Core
+{
+    public class LayerPropertyGroupUpdatingEventArgs : EventArgs
+    {
+        public LayerPropertyGroupUpdatingEventArgs(double deltaTime)
+        {
+            DeltaTime = deltaTime;
+        }
+
+        public double DeltaTime { get; }
+    }
+}