CA, add show/hide points preference
CA, add show/hide points preference to display only labels if wanted.
If only labels are displayed, they should be centered on the reference point coordinates.
This should be the default preference value.
Validation tests
- create a CA =>only labels must be drawn and using the rows/cols colors
- use the toggle button “show/hide point shapes” to show the point shapes
- tests the mouse over and item selection rendering
(from redmine: issue id 2033, created on 2017/02/10 by Sebastien Jacquot)