[c++] Fix bug in TaskSE3Equality: when expressing task quantities in world frame there was a mistake in the transform of the position error from local to world frame. Switch from log6 to log3 to avoid coupling between orientation error and translation error, which made task mask not work properly.

[python] Fix a few bugs introduced with recent changes to make ex_3 work with Talos and meshcat viewer.

[python] Update notebooks and scripts to use urdf files from example-robot-data. Update notebooks to use numpy.array instead of numpy.matrix. Cleaning up.

Add option in tsid_biped.py to specify contact motion constraints as costs rather than hard constraints.

Authored by: Aurélie Bonnefoy <abonnefoy@laas.fr>

Update all python script in the folder exercizes to use numpy.array rather than matrix (which is the new standard for eigenpy and pinocchio)

Authored by: Aurélie Bonnefoy <abonnefoy@laas.fr>

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.