Support calcInvKin for static link as working frame for REP Solver

[Levi-Armstrong]

Current the inverse kinematics solver only return a single working frame and the kinematics group only provided working frames relative to this link. This is only an issue when the working frame is an active link like in the robot with an external positioner kinematic arrangement. @marip8 mentioned it would be nice to still be able to solve IK in this case for static links. This would allow the user to generate solutions to find the best positioner solution that maximizes collision distance from the robot.

The proposed approach to solve this is to require that all inverse kinematics be able to return an IK solution relative to its base link which is a static link. I plan to update the documentation to reflect this and update the REP and unit test.