Renaming some classes

Here I have a suggestion list for different classes:

1. StatePinocchio → StateRobot
2. Cost(Data/Model)Pinocchio → Cost(Data/Model)Robot
3. Cost(Data/Model)PlacementVelocity → Cost(Data/Model)Motion
4. Cost(Data/Model)Position6D → Cost(Data/Model)SE3
5. Cost(Data/Model)Force6D → Cost(Data/Model)Wrench
6. Cost(Data/Model)Sum → Cost(Data/Model)Manager
7. Action(Data/Model)LQR → Action(Data/Model)
8. DifferentialAction(Data/Model) → DifferentialAction(Data/Model)ABA

Additionally, I would like to use:

• Dynamics instead of State
• Semantic description (e.g DDPSolver instead of SolverDDP)

Please let me know your thoughts! @nmansard @rbudhira