Nuttx now supports sh and source (.)
sh will open a new process for each invocation.
This means the child can not modify the parent
env. So we must use . to matain how nuttx worked.
Since rc.vehicle_setup is used in both we use
source and alis as we did with sh.
* add support for unmanned underwater vehicles:
* airframe uuv_generic + uuv_hippocammpus including mav_type = 12 for submarines
* mixer for UUVs with X-shaped thruster setup similar to quadcopter
* add module uuv_att_control for underwater robot attitude control
* add rc.uuv_defaults/apps for autostarting e.g. ekf2 and uuv_att_control app