use DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS by default for now,
until we find the issue with some failing test cases in btMultiBody
fix a crashing issue in MyMultiBodyCreator.cpp (uninitialized variable)
disable excessive debug printf in URDF2Bullet
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)
