Solver
This PR request contain few improvements in the solver structure and its unit-test. The changes are:
- Armijo-like condition for acceptance the line search
- Comparison between DDP solution and KKT solution (unit-test)
- Using data.f for integration, instead of creating internally a data for it.
- Simple tuning of mu for Value-function regulation.
All the changes were tested in the set of unit-tests, and in the DDP problem with the manipulator and quadruped robots.