Use kF_UseGjkConvexCastRaytest by default for raycast in PyBullet (it is more robust/accurate, but a bit slower)

Use 10*EPSILON, as suggested in Gino's paper:
http://www.continuousphysics.com/ftp/pub/test/files/physics/papers/jgt04raycast.pdf

src/BulletCollision/NarrowPhaseCollision/btSubSimplexConvexCast.cpp

@@ -72,11 +72,8 @@ bool	btSubsimplexConvexCast::calcTimeOfImpact(
 
 
 	btScalar dist2 = v.length2();
-#ifdef BT_USE_DOUBLE_PRECISION
-	btScalar epsilon = btScalar(0.0001);
-#else
-	btScalar epsilon = btScalar(0.0001);
-#endif //BT_USE_DOUBLE_PRECISION
+	btScalar epsilon = SIMD_EPSILON * 10;
+
 	btVector3	w,p;
 	btScalar VdotR;