[contrasting project] remove the restriction of maxima to winter. because i will focus only on snowfall so i don't really need that restriction

[contrasting project] generate plot for the trends in return levels for the winter extended. do the same for the distribution of wps. remove winter_maxima and summer_maxima in abstract_study.py

[contrasting project] fix memory issue that was happening while loading many precipitation studies. issue #300

[paper 2] rename safran precipitation total to safran precipitation. add snowfall, precipitation, and rainfall study classes for 1, 3, 5 and 7 days