[NUI] Implements a BorderWindow

[NUI] Implements a BorderWindow
1. Requirements :
 Like the desktop environment,
 - It should be possible to resize and move by adding a border area to the window.
 - By adding buttons to the border area, each button should have a minimize, maximize, and close function.
 - Border UI should be customizable.

2. interface IBorderInterface
 - User can configure border UI by inheriting IBorderInterface.

3. class DefautBorder is the default border UI.
 - User can also override the function by inheriting this DefaultBorder.

4. Sample
 - DefautBorder
```c#
  // If null is set for the second argument when creating a window, it is configured as DefaultBorder UI.
  subWindow = new Window("subwin", null, new Rectangle(20, 20, 800, 800), false);
```

 - CustomBorder
```c#
  class CustomBorder : DefaultBorder
  {
    public override voide CreateBorderView(View rootView)
    {
      // create custom border UI
      var custom = new View();
      rootView.Add(custom);
    }
  }

  void init()
  {
    CustomBorder border = new CustomBorder();
    var subWindow =  new Window("subwin", border, new Rectangle(60, 20, 800, 800), false);
  }
```