[refactor] rename folders for one/two fold fit. move the code for the anomaly into temperature_covariate.py

[refactor] move altitudes_studies.py. create trend test folder inside extreme_trend. deactivate one test for param_function that was crashing globally for unknown reason (but locally the test is working).

[projections] add mean merge function for the ensemble. fix max abs for median/mean visualizer. Fix OneFoldFitMerge that was given empty list as input.