presentation: Make OutputChooser unresizable

There is no particular reason for it to be resizable, and other dialogs
like properties and sharing are not resizable either.

https://bugzilla.gnome.org/show_bug.cgi?id=737580
presentation: Use a header bar

https://bugzilla.gnome.org/show_bug.cgi?id=737580
presentation: Ensure the builtin display is first in the list

This makes it consistent with Settings -> Displays.

https://bugzilla.gnome.org/show_bug.cgi?id=737580