[Thesis committee drawing] improve GEV non stationary plots.  rename ci_delta to ci_mle. catch some ci runtime exceptions. remove hatch/stripes drawing temporarily. fix unit for snow load. add new crocus classes & variable classes for snow load. modify conversion factor only for the new plots.

[SCM] add 3 consecutive nb_days as default argument. add this argument for SWE and SD. Also add a test to SCM study