This function generates the metal input script, processes each input results file, and runs the meta analysis
Inputs:
assoc_files : an array of association results files, like those generated in the single variant association pipeline, must have a column labeled "MAF" (Array[File], .csv or .tsv)
marker_column : column name in assoc_files with variant identifiers (string, default = snpID)
sample_column : column name in assoc_files for weighting of variants (string, default = n)
allele_effect_column : column name in assoc_files with effect allele (string, default = alt)
allele_non_effect_column : column name in assoc_files with non effect allele (string, default = ref)
pval_column : column in assoc_files with variant p-value (string, default = Score.pval)
effect_column : column in assoc_files with variant effect (string, default = Score.Stat)
out_pref : prefix for output filename (string)
separator : character that separates each input result file (string, default = COMMA [WHITESPACE, TAB])
analyze_arg : optional argument for other types of analyses (string, default = ZSCORE)
Outputs:
result_file : results per variant for all variants tested (.TBL)
metal_script : script that was generated as input to METAL (script.txt)
log_file : log file capturing standard error of running METAL (.log)
info_file : description of results_file columns, input files