merge python source trees

[nim65s]

Hi,

We have 2 source trees for python files:
https://github.com/stack-of-tasks/sot-torque-control/tree/master/python/dynamic_graph/sot/torque_control
https://github.com/stack-of-tasks/sot-torque-control/tree/master/src/dynamic_graph/sot/torque_control

I think we should remove the python/ one and move everything in src/.

[olivier-stasse]

👍 This will be consistent with the other repositories.