Combine scores merge

[davidbaines]

This update to combine_scores is designed to pull all the different Scores files into one Excel table. Where there are two or more scores files with a different set or order of columns they are combined into one dataframe so that the output is not on separate tabs in Excel.

This change should not affect any file other than combine_scores.py

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This change is 

[benjaminking]

@benjaminking reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @davidbaines)

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silnlp/common/combine_scores.py line 117 at r1 (raw file):

def clean_dataframe(df):
    cleaned_df = df.copy()
    cleaned_df = cleaned_df[~((cleaned_df['trg_iso'] == 'ALL') & (cleaned_df['chrF3++'].isna() | (cleaned_df['chrF3++'] == '')))]

It could be worth adding a comment to this line. It's not super obvious from reading it what the line is doing.