Core - Added ColorGradient type to use for.. gradients!

Core - Initialisation process no longer takes place in core constructor and is no longer async
UI - Fixed exceptions during init not being shown
Gradient editor - Started work on this

src/Artemis.UI.Shared/Converters/ColorGradientToGradientStopsConverter.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Globalization;
+using System.Windows.Data;
+using System.Windows.Media;
+using Artemis.Core.Models.Profile;
+using SkiaSharp;
+
+namespace Artemis.UI.Shared.Converters
+{
+    /// <inheritdoc />
+    /// <summary>
+    ///     Converts  <see cref="T:Artemis.Core.Models.Profile.ColorGradient" /> into a
+    ///     <see cref="T:System.Windows.Media.GradientStopCollection" />.
+    /// </summary>
+    [ValueConversion(typeof(ColorGradient), typeof(GradientStopCollection))]
+    public class ColorGradientToGradientStopsConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            var colorGradient = (ColorGradient) value;
+            var collection = new GradientStopCollection();
+            if (colorGradient == null)
+                return collection;
+
+            foreach (var c in colorGradient.Colors)
+                collection.Add(new GradientStop(Color.FromArgb(c.Color.Alpha, c.Color.Red, c.Color.Green, c.Color.Blue), c.Position));
+            return collection;
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            var collection = (GradientStopCollection) value;
+            var colorGradient = new ColorGradient();
+            if (collection == null)
+                return colorGradient;
+
+            foreach (var c in collection)
+                colorGradient.Colors.Add(new ColorGradientColor(new SKColor(c.Color.R, c.Color.G, c.Color.B, c.Color.A), (float) c.Offset));
+            return colorGradient;
+        }
+    }
+}