Add support for custom themes in chardonnay

Source/LibationAvalonia/Dialogs/ThemePickerDialog.axaml

@@ -0,0 +1,70 @@
+<Window xmlns="https://github.com/avaloniaui"
+		xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+		xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+		xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+		mc:Ignorable="d" d:DesignWidth="450" d:DesignHeight="450"
+		Width="450" Height="450"
+		x:Class="LibationAvalonia.Dialogs.ThemePickerDialog"
+		Title="Theme Editor">
+	<Grid
+		RowDefinitions="*,Auto">
+		<DataGrid
+			GridLinesVisibility="All"
+			Margin="5"
+			IsReadOnly="False"
+			ItemsSource="{Binding ThemeColors}">
+			<DataGrid.Columns>
+
+				<DataGridTemplateColumn Width="Auto" Header="Color">
+					<DataGridTemplateColumn.CellTemplate>
+						<DataTemplate>
+							<ColorPicker
+								IsHexInputVisible="True"
+								Color="{Binding ThemeColor, Mode=TwoWay}" />
+						</DataTemplate>
+					</DataGridTemplateColumn.CellTemplate>
+				</DataGridTemplateColumn>
+				
+				<DataGridTextColumn
+					Width="*"
+					Binding="{Binding ThemeItemName, Mode=TwoWay}"
+					Header="Theme Item"/>
+
+			</DataGrid.Columns>
+
+		</DataGrid>
+		<Grid
+			Grid.Row="1"
+			ColumnDefinitions="Auto,Auto,Auto,*,Auto">
+			
+			<Grid.Styles>
+				<Style Selector="Button">
+					<Setter Property="Height" Value="30" />
+					<Setter Property="Padding" Value="20,0" />
+					<Setter Property="Margin" Value="5" />
+				</Style>
+			</Grid.Styles>
+			
+			<Button
+				Grid.Column="0"
+				Content="Cancel"
+				Command="{Binding CancelAndClose}" />
+			
+			<Button
+				Grid.Column="1"
+				Content="Reset"
+				Command="{Binding ResetColors}" />
+			
+			<Button
+				Grid.Column="2"
+				Content="Defaults"
+				Command="{Binding LoadDefaultColors}" />
+			
+			<Button
+				Grid.Column="4"
+				Content="Save"
+				Command="{Binding SaveAndCloseAsync}" />
+
+		</Grid>
+	</Grid>
+</Window>