Simulate claw in Gazebo

[doruphin]

Add support for a claw opening and closing in Gazebo with proper physics simulation

Notes

• We have the claw models in Onshape, you may have to ask the actuators team for a model that opens and closes though
• If we don't have the ability to control the claw from ROS yet, you can just make a temporary topic to see it move

Task

• Add the claw to the steelhead model
• Simulate the grabbing in Gazebo