Loading and Unloading DockingManager

Test Load/Unload of DockingManager with FloatingWindows

1. Open the MainWindow.xaml file of any test application that supports storage, retrieval, and restore of FloatingWindow positions (eg: MLib_Test). Put the DockingManager control into a tab control and start the application.

<TabControl Grid.Row="1">
    <TabItem Name="tab1" Header="tab 1">
        <avalonDock:DockingManager x:Name="dockManager"
            ...
        </avalonDock:DockingManager>
    </TabItem>
    <TabItem Name="tab2" Header="tab 2">
        <TextBlock Text="tab2"></TextBlock>
    </TabItem>
</TabControl>

2. Start application and undock any panel (drag document or ancharable into a FloatingWindow position)
3. Switch to tab 2
4. Switch back to tab 1

Expectation: The floating window with undocked panel re-appears when tab1 is re-activated. see #51