c_curve and lc_extrap output format

[AndreaMariani-AM]

Hi,

I'm using preseq v3.1.1 and the output format of c_curve and lc_extrap i think could be improved. Given that they are frequently used together, c_curve output column names are all in lowercase, whereas the output of lc_extrap is in uppercase. Especially the first column (total_reads vs TOTAL_READS) could benefit from the same formatting