Implementation DataGenerator Class

Implement the DataGenerator class form @kleinert1 origin repo. Improve wherever it is possible. A complete implementation includes tests and a little documentation. This is right now a very long list. Therefore, first check which methods are required and how to refactorise / restructure the module to have a cleaner view / thinner structure. All modules have been removed from this class, because there was no reason to be inside the DataGenerator class. They need to be implemented in other classes or as function (e.g. class for plotting, post-processing, ...).

• __init__
  • code
  • tests
  • docs
• __repr__
  • code
  • tests
  • docs
• __len__
  • code
  • tests
  • docs
• __iter__
  • code
  • tests
  • docs
• __next__
  • code
  • tests
  • docs
• __getitem__
  • code
  • tests
  • docs
• get_data_generator
  • code
  • tests
  • docs
• get_key_representation -> get_station_key
  • code
  • tests
  • docs
• rescale
• ols_reshape_xarray_to_np
• ols_prep
• ols_model
• make_prediction
• check_path_and_create
• clim_deco
• calc_RMSE
• RMSE
• threshold_setup
• thresholds_float
• threshold_nearest
• calc_thresholds
• skill_scores
• hist_settings
• create_plots
• plot_monthly_summary