Add preparation for DeepMimic humanoid environment, replicating parts of https://github.com/xbpeng/DeepMimic
Loading humanoid.urdf and applying motion action: examples/pybullet/gym/pybullet_envs/mimic/humanoid.py
Loading MotionCapture data: examples/pybullet/gym/pybullet_envs/mimic/motion_capture_data.py
Little test: examples/pybullet/gym/pybullet_envs/mimic/humanoid_test.py
