External axis

[danwahl]

Before submitting this PR into master please make sure:

If you added a new robot model:

• you extended the table of verified data in README.md with the new model
• you extended the CMakeLists.txt of the appropriate moveit configuration package with the new model
• you added a test_<robot_model>.launch.py and after launching the robot was visible in rviz
• you added a <robot_model>_joint_limits.yaml file in the config directory (to provide moveit support)

If you modified an already existing robot model:

• you checked and optionally updated the table of verified data in README.md with the changes
• you have run the test_<robot_model>.launch.py and the robot was visible in rviz

Short description of the change