[contrasting] add histogram for model repartition & evolution of trends. improve preliminary_analysis.py

[contrasting] consider also the stationary model for selection. consider a level of altitude only if at least 2 altitudes are present & the reference altitude is present.

[contrasting] improve pointwise_gev_study_visualizer.py with a linear regression against the altitude. modify the _maxima_gev depending on the fit method

[contrasting] add a pre-computed of the max_abs value for the shape parameter & for the various moments

[contrasting] add temporal covariate argument to the margin model class, so that we could use the global temperature as covariate.

[contrasting] display individual model fitted with all data (300-4800). Display only the best non-stationary model if it passes the Anderson fit test.

[contrasting] add default pval equal to zero in gnFit (to avoid the program to crash when called by python). refactor anderson test. add anderson test by default for the one fold analysis.

[contrasting] harmonize gumbel altitudinal models. create plot_total_aic.py. remove exception for model with infinite aic.

[contrasting] add quadratic & cross terms Gumbel altitudinal models & fix a recurrent bug that happenning when checking the AIC value

[contrasting] add Gumbel altitudinal models. But so far only the first three models are passing tests (models with quadratic & cross terms are crashing)

This includes models that combine some quadratic aspect & a cross term.
Remove random test

the selection for the model with minimal aic only takes into account models with with finite aic (there are often several models with infinite aic)