* [bugfix] Included the velocity limits in the talos-legs model

to ease data finding in C++
ref https://github.com/stack-of-tasks/pinocchio/issues/965

renamed files

PYTHON_INSTALL_ON_SITE does the PYTHON_BUILD and the INSTALL, but they
require to have the same arguments. Then, we have to put the CMakeLists
in a parent folder of the module, as `python`, or `bindings/python`.

from https://github.com/ros-industrial/universal_robot/tree/kinetic-devel/ur_description

to comply with other packages

to ease robotpkg packaging

s.t. Pinocchio can depend on the data, and we can provide simultaneously
several python versions