Abstract out the Jacobian properties of BodyNodes

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It is desirable to have forward/inverse kinematic concepts that are independent of dynamic properties (such as mass and moment of inertia).

An example is the Task Space Region Chain concept which performs inverse kinematics on a kinematic chain which is not necessarily a real, physical, dynamic, or simulatable chain of BodyNodes.

We can shift the BodyNode Jacobian functionality into a base class (named something like JacobianBase or JacobianEntity) and allow Joints to have a JacobianBase child rather than a BodyNode child. Some Joint functionality might have to be shifted into the BodyNode class.

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Finished in #461