Torque control of the Kinova Gen 3

[my-rice]

1. Joint-space PD control

• Implement a PD controller acting on joint positions using joint position commands.
• Implement a PD with gravity compensation using joint torques commands.
• Validate behavior on the Kinova Gen 3 robot.

2. Operational (task) space PD control

• Extend the controller to operate in task/operational space (e.g., end-effector/foot positions and velocities).
• Use kinematics/Jacobian mapping to convert task-space errors into joint torques/commands.
• Validate behavior in task space

[my-rice]

I implemented all items described in this issue in the feature/arm_control branch.

• Joint-space PD control is implemented (position-command PD) (I deleted it. It was just for testing the module)
• Joint-space PD + gravity compensation is implemented using joint torque commands. (I commented it out. It was just for testing the module)
• Validated behavior on the Kinova Gen3
• Task/operational-space PD control is implemented with kinematics/Jacobian mapping to joint torques

The task-space controller is currently named cartesian_motion_controller.
For redundant robots, I added a null-space behavior that tracks a hard-coded joint configuration, but it needs to be configurable.