[pybullet] updated pybullet_quickstartguide.pdf
Fail clearly (assert, return BT_INFINITY) if link index is out of range for btMultiBody methods localPosToWorld,worldPosToLocal,localDirToWorld,worldDirToLocal.
pybullet getConstraintInfo
Fix warnings due to Mac OSX 10.12 upgrade (with backward compatibility)
set a default camera targets for each demo. note that it is only reset when switching to a different demo, so you can restart at your chosen location.
no OpenCL pairbench drawing in OpenGL2 (there is no VBO available etc)
