Try and stress the combinations of DeriveDisplayOrder and UnifiedHelpMessage
along with propagating them to subcommands and explicitly setting a display
order.
The new tests
derive_order_subcommand_propagate
unified_help_and_derive_order_subcommand_propagate
unified_help_and_derive_order_subcommand_propagate_with_explicit_display_order
are currently failing because of bug #706.
