atlas model: remove rpy on {left,right}_led_frame, as "rotation of body frames not yet supported" by RBDL

lwr: use the other world link, to fix RBDL "Error while processing joint 'arm_world_joint': parent link 'world' could not be found.

sorry for the big commit -_-

Basis to run ABA & RNEA on Pinocchio & RBDL with the URDF models provided by Pinocchio