Set solver's working TF frame as the kinematic chain's base frame and not the _world_ frame

[SimonGiampy]

Currently the IK solver transforms all poses in the world frame, and computes the solution candidates in the world frame. It would be useful instead if it avoids transformations at all, and if the input target poses are expressed in the kinematic chain's base frame, as well as all intermediate computations.
It would be more efficient and avoid possible bugs