fixed usage for only one scenario year -> removed drop() when reading in files and adjusted subsequent apply() calls

now the full files_list will be checked, while you can also add other output names via replace_input_file_names

added function argument replace_input_file_names to handle different file names without the need to change the metric_files.yml file

varnames are not needed anymore - all handled through metrics_file.yml + changed lat/lon handling, will now be saved in the object + some minor changes to plotting functions

added new variable biocol_abs_frac as overtime biocol, but taking the absolute before adding all cells of one timestep up