Finalize PR 16 and add Panda wrapper

[Kotochleb]

Description

This PR is a continuation of #16. Compared to previous PR following changes were made:

• URDF is now based on the one found in example-robot-data.
• MuJoCo file was generated based on the URDF file.
• Meshes were added.
• Removed additional formatting in places unrelated to the PR.
• Examples were added.
• Branch was rebased to newest main branch on the upstream.

In the models provided by this PR there is one difference compared to example-robot-data. Visual meshes were converted from Collada format (.dae) to STL format.

Also, there is a controversial bit I wanted to raise, as URDF of Panda in example-robot-data includes 9 controllable joints with both finder lips being treated as separate joints. @skleff1994 do you think the finger lips should be locked or kept as they are with an option to disable them with locked_joints_names?

How I Tested

All examples with Pinocchio, Bullet and MuJoCo were tested, tho they required some changes.

I fulfilled the following requirements

• All new code is formatted according to our style guide (for C++ run clang-format, for Python, run flake8 and fix all warnings).
• All new functions/classes are documented and existing documentation is updated according to changes.
• No commented code from testing/debugging is kept (unless there is a good reason to keep it).