Expose PyBullet.calculateVelocityQuaternion, getAxisAngleFromQuaternion, getQuaternionFromAxisAngle, getDifferenceQuaternion

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

examples/pybullet/gym/pybullet_envs/mimic/motion_capture_data.py

@@ -0,0 +1,19 @@
+import json
+
+class MotionCaptureData(object):
+  def __init__(self):
+    self.Reset()
+
+  def Reset(self):
+    self._motion_data = []
+
+  def Load(self, path):
+    with open(path, 'r') as f:
+      self._motion_data = json.load(f)
+
+  def NumFrames(self):
+    return  len(self._motion_data['Frames'])
+
+  def KeyFrameDuraction(self):
+  	return self._motion_data['Frames'][0][0]
+