Redefined robustness measure

The robustness measure is redefined in which a unimodal function with high conditioning and two multimodal with good and weak global structure are adopted to test performance of the solvers. Specifically, the twisted valley function, the rotated Rastrigin's function, and the multimodal version of rosenbrock function are adopted for test functions. In addition, every solver is re-optimized and updated. Finally, the refactering of optimization has been done in which any new solver optimization becomes very easy to implement.