Homogeneization of notation in python example

cpp/src/LQT.cpp

data/convert_mat_to_numpy.py

matlab/iLQR_manipulator_CoM.m

python/IK.py

python/IK_num.py

python/iLQR_manipulator.py

python/iLQR_manipulator_CP.py

python/iLQR_manipulator_CoM.py

python/iLQR_obstacle.py