Support for CasADi and Python interfacing

[Pedro-Roque]

What's in the title :smile: Readme was updated accordingly.

[Jaeyoung-Lim]

@Pedro-Roque Thanks for the changes!

I tried to follow the instructions, but I think there is some local path in the astrobee example

Running simulation....
Traceback (most recent call last):
  File "nodes/astrobee_demo.py", line 62, in <module>
    main()
  File "nodes/astrobee_demo.py", line 56, in main
    t, y, u = sim_env_tracking.run(x0)
  File "/home/jaeyoung/.local/lib/python3.8/site-packages/px4_mpc/simulation/basic_environment.py", line 45, in run
    u, error = self.controller(x, i * self.dt)
  File "/home/jaeyoung/.local/lib/python3.8/site-packages/px4_mpc/controllers/mpc.py", line 390, in mpc_controller
    x_traj = self.model.get_trajectory(
  File "/home/jaeyoung/.local/lib/python3.8/site-packages/px4_mpc/models/astrobee.py", line 164, in get_trajectory
    tmp = np.loadtxt('/home/roque/trajectory_quat.txt', ndmin=2)
  File "/home/jaeyoung/.local/lib/python3.8/site-packages/numpy/lib/npyio.py", line 1042, in loadtxt
    fh = np.lib._datasource.open(fname, 'rt', encoding=encoding)
  File "/home/jaeyoung/.local/lib/python3.8/site-packages/numpy/lib/_datasource.py", line 193, in open
    return ds.open(path, mode, encoding=encoding, newline=newline)
  File "/home/jaeyoung/.local/lib/python3.8/site-packages/numpy/lib/_datasource.py", line 532, in open
    raise FileNotFoundError(f"{path} not found.")
FileNotFoundError: /home/roque/trajectory_quat.txt not found.

Am I missing something?

[Pedro-Roque]

I'll do the PR with the Quad example, with this fixed.