data_parser.py could be improved

[robfairh]

1- I believe the function make_plots in data_parser.py could be deleted. If my reading is correct, the functions make_emissions_plots and make_capacity_plots do together what make_plots does.

2- Also, the following lines could be a for loop:

            # create dataframes
            df_elc = create_dataframe(datalines, var, sector='elc')
            df_ind = create_dataframe(datalines, var, sector='ind')
            df_vcl = create_dataframe(datalines, var, sector='vcl')
            plot = plots_dict[var]
            plot(dataframe=df_elc,
                 variable=var,
                 scenario=scenario,
                 sector='elc',
                 save=to_save)
            plot(dataframe=df_ind,
                 variable=var,
                 scenario=scenario,
                 sector='ind',
                 save=to_save)
            plot(dataframe=df_vcl,
                 variable=var,
                 scenario=scenario,
                 sector='vcl',
                 save=to_save)