Add type KDL-related types: jacobian/inertia/coriolis/gravity/velocity

[ndehio]

A type for jacobian would be beneficial, as well as for inertia/coriolis/gravity for the inverse dynamics model. Also CartesianVelocity would be nice. At the moment I use pure Eigen instead.
Eigen::MatrixXf jacobian;
Eigen::MatrixXf inertia;
Eigen::VectorXf gravity;
Eigen::VectorXf coriolis;
Eigen::VectorXf velocity;

What do you think about these types?

[xwavex]

i totally agree about these types; we need them!