add confirmation dialogue for `xfce4-display-settings --minimal`

Submitted by Liv

Assigned to Jérôme Guelfucci

Link to original bug (#13309)

Description

Changes in xfce4-display-settings --minimal are generally just as fragile as changes in the main xfce4-display-settings: If you're not paying attention or something doesn't work as expected, you may end up without ANY active or usable screen. Having a confirmation dialogue (as for the main Display settings) would help avoid such issues...

This is somewhat related to Bug 11479.

Version: 4.12.0