Reopened Unassigned: PropertyGrid.EditorDefinitions Broken [20120]

Not sure how this hasn't been noticed, but EditorDefinitions no longer work in 2.0. To reproduce, take the following code and stick it in a project:

__MainWindow.xaml__:
```
<Window x:Class="PropertyGridTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
Title="PropertyGrid Test">
<xctk:PropertyGrid x:Name="propertyGrid">
<xctk:PropertyGrid.EditorDefinitions>
<xctk:EditorDefinition TargetType="{x:Type sys:String}">
<xctk:EditorDefinition.EditorTemplate>
<DataTemplate>
<Border Background="Red">
<TextBlock>Here!</TextBlock>
</Border>
</DataTemplate>
</xctk:EditorDefinition.EditorTemplate>
</xctk:EditorDefinition>
</xctk:PropertyGrid.EditorDefinitions>
</xctk:PropertyGrid>
</Window>
```
__MainWindow.xaml.cs__:
```
using System.Windows;

namespace PropertyGridTest
{
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();

this.propertyGrid.SelectedObject = new Data();
}
}

public class Data
{
public string Name
{
get;
set;
}

public int Age
{
get;
set;
}
}
}
```
Then install 1.9.0:
```
Install-Package Extended.Wpf.Toolkit -Version 1.9.0
```
Run this and you will see a red border for the name entry, as expected. Now do this:
```
Uninstall-Package Extended.Wpf.Toolkit
Install-Package Extended.Wpf.Toolkit -Version 2.0.0
```
Run this again and you won't see the custom editor.