having a command ID in them doesn't really make sense

Pair-Programmed-With: Randy Mackay <rmackay9@yahoo.com>

This command is only used to get the vehicle home (or to a rally point)
after the mission has completed

non_nav_command_ID and next_nonnav_command variables removed

fixes for AP_Mission integration

Pair-Programmed-With: Randy Mackay <rmackay9@yahoo.com>

good for ground steering on larger aircraft

thanks to Mike McCauley