Add generic TreeView class

EstusShots.Gtk/Controls/DataColumn.cs

@@ -0,0 +1,16 @@
+namespace EstusShots.Gtk.Controls
+{
+    public class DataColumn
+    {
+        public string PropertyName { get; set; }
+        
+        public string Title { get; set; }
+
+        public DataColumn()  { }
+
+        public DataColumn(string propertyName)
+        {
+            PropertyName = propertyName;
+        }
+    }
+}