[EXTREME ESTIMATOR] refactor margin_fits folder. extreme estimator folder. and extreme_models folder

[EXTREME ESTIMATOR][MARGIN MODEL] refactor linear margin model folder organization. refactor names in univariate trend analysis

[COORDINATE] refactor starting year & df_temporal_coordinates. to normalize the same way any temporal covariate. So that each fit has the same type of normalized data as input. add multiple transformation.

[EXTREME ESTIMATOR][MARGIN MODEL] add temporal linear margin model test. check that starting point are taken into account.

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

[EXTREME FIT] After any Spatial Extreme fit, create an object ResultFromFit, refactor code accordingly