Add Euler integration to python binding.
Add Euler integration to python binding.

jrl-umi3218/RBDyn,gergondet/RBDyn,gergondet/RBDyn,jrl-umi3218/RBDyn,jrl-umi3218/RBDyn,gergondet/RBDyn,gergondet/RBDyn,jrl-umi3218/RBDyn,gergondet/RBDyn