TracIK Implementation for `kinematics_interface`

[jcarpinelli-bdai]

The ros2_control project has a kinematics_interface that is defined by four methods: calculate_jacobian, calculate_link_transform, convert_joint_deltas_to_cartesian_deltas, and convert_cartesian_deltas_to_joint_deltas. They also provide an implementation using KDL. Forking this KDL plugin, and modifying it to use TracIK instead, should be relatively straightforward! I may be able to help with this, if it is a desired feature.