Adding Franka Emika Panda Example

[nataliya-dev]

• Adding Franka Emika Panda urdf and mesh files.
• Created panda_fr3.py which is based on the kinova_gen3.py script to perform trajectory optimization with the panda arm and a large ball.
• Updating the readme file with the description of the new file.
• Retains the modular properties of this repo, with each script being self contained, however, I do see the benefit of putting together the two manipulator files together to reduce duplicate code.