BUG #13784. Cleaning up xy-chart settings dialog.

- Removing "Show Axis". The charts manage the visbility of axis automatically
  works better.
- Cleaning up the settings dialog a little: merged the "Title" page into the
  Axis' settings page.

Change-Id: Ie757bddc1fae5ebf160bd8e8e90afd33a8a4518d
Merge topic '13784_cleanup_chart_settings_dialog' into next

e04bb8a BUG #13784. Cleaning up xy-chart settings dialog.