add yapf style and apply yapf to format all Python files

This recreates pull request #2192

examples/pybullet/examples/signedDistanceField.py

@@ -1,15 +1,14 @@
 import pybullet as p
-import pybullet 
+import pybullet
 import time
 p.connect(p.GUI)
 p.loadURDF("toys/concave_box.urdf")
-p.setGravity(0,0,-10)
-for i in range (10):
-	p.loadURDF("sphere_1cm.urdf",[i*0.02,0,0.5])
+p.setGravity(0, 0, -10)
+for i in range(10):
+  p.loadURDF("sphere_1cm.urdf", [i * 0.02, 0, 0.5])
 p.loadURDF("duck_vhacd.urdf")
-timeStep = 1./240.
+timeStep = 1. / 240.
 p.setTimeStep(timeStep)
 while (1):
-	p.stepSimulation()
-	time.sleep(timeStep)
-	
+  p.stepSimulation()
+  time.sleep(timeStep)