Add density correction string to 1d filenames

[nicholebarry]

Currently, the density correction string is added to the legend. I think it would be beneficial to be added in addition to the file name so that we can make various density cuts without overwriting the plot files. Example (plot file name: fhd_nb_gaussbeam_1fits_dist_test_zenith_fullimg_dft_averemove_swbh_no_horizon_wedge_kperplambda10-30_1dkpower.png):