Added shared UI library and finished the ColorPicker

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

@@ -0,0 +1,39 @@
+using System;
+using System.Globalization;
+using System.Windows.Data;
+using System.Windows.Media;
+
+namespace Artemis.UI.Shared.Converters
+{
+    /// <inheritdoc />
+    /// <summary>
+    ///     Converts <see cref="T:System.Windows.Media.Color" /> into <see cref="T:System.String" />.
+    /// </summary>
+    [ValueConversion(typeof(Color), typeof(string))]
+    internal class ColorToStringConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return value?.ToString();
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            try
+            {
+                if (string.IsNullOrWhiteSpace((string) value))
+                    return default(Color);
+
+                var color = ColorConverter.ConvertFromString((string) value);
+                if (color is Color c)
+                    return c;
+
+                return default(Color);
+            }
+            catch (FormatException)
+            {
+                return default(Color);
+            }
+        }
+    }
+}