[HYPERCUBE VISUALIZER] fix big issue with respect to the "best year", take the year that minimizes the nllh

[SCM][HYPERCUBE] refactor trend analysis. use change of point test instead of tren test for the hypercube.

[SCM][HYPERCUBE] improve labelling of all the graphs. add test strength display in the spatial case.

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

[SCM][HYPERCUBE] Create Hypercube object with MultiIndex. Modify @cached_property in utils (from a library and seems to a bit faster). added some parallelization for trend test type in study_visualizer.

[SCM][NON STATIONARY TREND] modify some display parameter. add pre loaded LATITUDE & LONGITUDE to scm_constants file. remove massif file.

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

[EXTREME ESTIMATOR][MARGIN MODEL] add ismev gev fit. and refactor. add result_from_fit abstract class.

[EXTREME ESTIMATOR][MARGIN MODEL] add stationary/non-stationary margin model. fix margin formula (in the temporal case when we want a dependency on a single parameter for instance). add margin function with starting point