Convert all python scripts from python 2 to python 3 using automatic tool 2to3. Stop using deprecated pinocchio function in test_Formulation.py

* [notebooks] Fix waist task, add the update of the waist trajectory in the loop, improve gains and add beginning of documentation, end documentation, add global distpackages to python path

[notebooks] Fix waist task. Add the update of the waist trajectory in the loop. Improve gains and add documentation.

ref https://github.com/stack-of-tasks/pinocchio/issues/849