Layer brushes - Added RGB.NET-based layer brushes

Layer brushes - Added sample RGB.NET-based color brush
Layer properties - Save on gradient edit dialog close
Layer properties - Fix layer brush keyframes not working after changing layer brush

src/Artemis.UI.Shared/Controls/GradientPicker.xaml.cs

@@ -1,6 +1,7 @@
 using System;
 using System.ComponentModel;
 using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Input;
@@ -8,6 +9,7 @@ using Artemis.Core.Models.Profile;
 using Artemis.Core.Models.Profile.Colors;
 using Artemis.UI.Shared.Annotations;
 using Artemis.UI.Shared.Services.Interfaces;
+using Stylet;
 
 namespace Artemis.UI.Shared.Controls
 {
@@ -19,6 +21,9 @@ namespace Artemis.UI.Shared.Controls
         private static IGradientPickerService _gradientPickerService;
         private bool _inCallback;
 
+        public event EventHandler DialogOpened;
+        public event EventHandler DialogClosed;
+
         public GradientPicker()
         {
             InitializeComponent();
@@ -77,7 +82,12 @@ namespace Artemis.UI.Shared.Controls
 
         private void UIElement_OnMouseUp(object sender, MouseButtonEventArgs e)
         {
-            GradientPickerService.ShowGradientPicker(ColorGradient, DialogHost);
+            Execute.OnUIThread(async () =>
+            {
+                OnDialogOpened();
+                await GradientPickerService.ShowGradientPicker(ColorGradient, DialogHost);
+                OnDialogClosed();
+            });
         }
 
         #region Static WPF fields
@@ -92,5 +102,15 @@ namespace Artemis.UI.Shared.Controls
             EventManager.RegisterRoutedEvent(nameof(ColorGradient), RoutingStrategy.Bubble, typeof(RoutedPropertyChangedEventHandler<ColorGradient>), typeof(GradientPicker));
 
         #endregion
+
+        protected virtual void OnDialogOpened()
+        {
+            DialogOpened?.Invoke(this, EventArgs.Empty);
+        }
+
+        protected virtual void OnDialogClosed()
+        {
+            DialogClosed?.Invoke(this, EventArgs.Empty);
+        }
     }
 }