title: WPF - ScrollViewer with fixed header/row
body: <p>What is the easiest way to create ScrollViewer with fixed header (control that always stays at the top ignoring the scroll), but which still scrolls horizontally.</p>
  
  <p>Should I write my own ScrollViewer template with header above ScrollContentPresenter, and move it when horizontal scroll value changes, or maybe it's better to put header inside ScrollViewer and move it vertically? Or maybe there is a lot better way to achieve this...</p>