title: Increase the spacing between TreeViewItems in a TreeView
body: <p>Im working with a TreeView in WPF.
  What I have is :-</p>
  
  <p>TreeRoot
  -TreeViewItem1
  -TreeViewItem2
  -TreeViewItem3
  -TreeViewItem4</p>
  
  <p>What I want is </p>
  
  <p>TreeRoot
  -TreeViewItem1</p>
  
  <p>-TreeViewItem2</p>
  
  <p>-TreeViewItem3</p>
  
  <p>-TreeViewItem4</p>
  
  <p>So, Is there a way to increase the spacing between the TreeViewItems</p>