title: Display marks in contour points
body: <p>I create a single contour and add it to the chart, add points with label text and also subscribe to the GetSeriesMark event, but the text is not displayed, and the event never gets fired</p>
  
  <pre><code>Contour contour1 = new Contour();
  contour1.IrregularGrid = true;
  // 
  // contour1
  contour1.Brush.Color = Color.FromArgb(68, 102, 163);
  contour1.ColorEach = false;
  contour1.EndColor = Color.FromArgb(192, 0, 0);
  contour1.FillLevels = checkEditFillLevels.Checked;
  // 
  // 
  contour1.Marks.Style = MarksStyles.Label;
  contour1.Marks.Visible = true;
  //
  //
  contour1.NumLevels = 8;
  contour1.PaletteMin = 0;
  contour1.PaletteStep = 0;
  contour1.PaletteStyle = PaletteStyles.Pale;
  // 
  // 
  contour1.Pen.Color = Color.FromArgb(192, 192, 192);
  contour1.Pen.Style = DashStyle.Dot;
  // 
  // 
  contour1.Pointer.HorizSize = 2;
  // 
  // 
  contour1.Pointer.Pen.Visible = false;
  contour1.Pointer.Style = PointerStyles.Rectangle;
  contour1.Pointer.VertSize = 2;
  contour1.Pointer.Visible = true;
  contour1.StartColor = Color.FromArgb(255, 255, 192);
  contour1.Title = "contour1";
  </code></pre>
  
  <p>Adding points is done with this</p>
  
  <pre><code>contour1.Add(x, y, z, "My Point 1");
  </code></pre>
  
  <p>Is there a way to display marks on the exact points in the Contour, and moreover is there a way to display marks only on specific points in the Contour (some points are actual data, others are made using interpolation to be able to show the contour)?</p>