Update underlying data field when related object is updated.

If the selected Library Document is out-of-range throw a specific error
Don't fail if the user clicks on open space in the BookMark list
Added property to provide a right margin (RTBMargin) between the RichTextBox and the StepItem

PROMS/Volian.Controls.Library/DisplayBookMarks.cs

@@ -113,7 +113,8 @@ namespace Volian.Controls.Library
 		private void lbxBookMarks_Click(object sender, EventArgs e)
 		{
 			MostRecentItem itm = lbxBookMarks.SelectedValue as MostRecentItem;
-			MyDisplayTabControl.OpenItem(itm.MyItemInfo);
+			if(itm != null)
+				MyDisplayTabControl.OpenItem(itm.MyItemInfo);
 		}
 		#endregion
 	}