[contrasting] aic and bic test ok for my first model combining a linearity in 2 different coordinates.

[contrasting] fix polynomial_margin_model.py creation. extend the form_dict for spatio temporal models.

[contrasting] add quadratic model for gumbel/gev and location/scale. modify code for the name of the models

[exceeding] add full diagnositic plot (qqplot & intensity plots) for gumbel stationary & add gumbel gof tests from r package

[exceeding] add full diagnositic plot (qqplot & intensity plots) for gumbel stationary & add gumbel gof tests from r package

[refactor] refactor main fitting function: by default, we fit without starting value, then we try several time with the start value