add a new function:
hra_programs.console.usage.merge_xlsx.merge_xls_by_column(output_xls,
sheet_name, 	output_column_idx, source_csv_files_mask, separator)
to merge external data with a xls file where a index column number is
defined by parameter named output_column_idx parameter

change name of the function merge_xls into merge_xls_by_index_file