连接线修改，为支持改变连接点做准备

Util.DiagramDesigner/UserControls/PointContainer.xaml

@@ -0,0 +1,14 @@
+<ItemsControl x:Class="Util.DiagramDesigner.PointContainer"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
+             xmlns:local="clr-namespace:Util.DiagramDesigner"
+             mc:Ignorable="d" 
+             d:DesignHeight="450" d:DesignWidth="800">
+    <ItemsControl.ItemsPanel>
+        <ItemsPanelTemplate>
+            <Canvas x:Name="rootCanvas"/>
+        </ItemsPanelTemplate>
+    </ItemsControl.ItemsPanel>
+</ItemsControl>