Default App: xdiagnose

[Jeremy Bicha]

The GNOME Activities Overview makes default installed apps much more
prominent so any app installed by default should work and be generally
useful.

xdiagnose does not work with GNOME on Wayland (LP: #1616742) because
of the pkexec issue I mentioned in a separate thread on this list.

The only Ubuntu flavors that include xdiagnose in 17.04 are Ubuntu
(Unity), Ubuntu Budgie and Ubuntu Kylin.

Maybe whatever useful parts of the app should be moved to another
package or app?

Jeremy