[SCM][HYPERCUBE] Add multiprocessing by default for abstract study. re-activate test_SCM_study which are now fast enough. fix issue with total precipitation variable. AltitudeHypercubeVisualizer first visualization.

[SCM][HYPERCUBE] Add multiprocessing when loading abstract study. Refactor abstract variable and all variables accordinlgly.

[EXTREME ESTIMATOR] add max iteration argument for any R fit. also add some verbose for trend tests experiments.

[SCM] add permutation which correspond to the sum of rainfall & snowfall. add test based on Durand paper.

[SAFRAN] move safran directory inside experiment directory, add safran visualizer. add smooth marginal estimation & full estimation