Update centroidal planner

1. The `SimpleDynamicsFullKinematicsPlanner` used deprecated code in `NonlinearProgram`. Update the planner to the newest version.
2. Add the example for Atlas jumping on flat ground, with both the planning code and the simulation
3. Restructure `SimpleDynamicsFullKinematicsPlanner` code, now it exposes fewer methods to the user
4. Add the code to plan centroidal dynamics only for the object being grasped. Also include the wrench for grasping, and a constraint to specify fixed position in a body frame.
5. Add gradient computation in `rpydot2angularvel` and `rpy2rotmat`
We should probably add documentation for `plant`.