Added layer properties to core and hooked it up with the UI

Implemented timeline caret scrolling logic
Added special treeview style for the layer properties tree

src/Artemis.UI/Extensions/TreeViewItemExtensions.cs

@@ -0,0 +1,24 @@
+using System.Windows.Controls;
+using System.Windows.Media;
+
+namespace Artemis.UI.Extensions
+{
+    public static class TreeViewItemExtensions
+    {
+        public static int GetDepth(this TreeViewItem item)
+        {
+            TreeViewItem parent;
+            while ((parent = GetParent(item)) != null)
+                return GetDepth(parent) + 1;
+            return 0;
+        }
+
+        private static TreeViewItem GetParent(TreeViewItem item)
+        {
+            var parent = VisualTreeHelper.GetParent(item);
+            while (!(parent is TreeViewItem || parent is TreeView))
+                parent = VisualTreeHelper.GetParent(parent);
+            return parent as TreeViewItem;
+        }
+    }
+}