Show message about missing implementation.

Refers to #2

ATXTray/AutoTxTray.cs

@@ -176,7 +176,8 @@ namespace ATXTray
                 DefaultDirectory = _config.SourceDrive
             };
             if (dirDialog.ShowDialog() == CommonFileDialogResult.Ok) {
-                MessageBox.Show("Directory\nselected:\n\n" + dirDialog.FileName,
+                MessageBox.Show("Directory\nselected:\n\n" + dirDialog.FileName +
+                    "\n\nWARNING: adding new transfers is NOT YET IMPLEMENTED!",
                     "New transfer confirmation", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
             }
         }