Convert flag_series into a boolean DataFrame indicating which checks the flags represent.

Parameters:flag_series (pandas.Series) – Integer series of validated quality flags
Returns:pandas.DataFrame – Columns are keys of BITMASK_DESCRIPTION_DICT and values are booleans indicating if the input flag corresponds to the given check. An additional column, NOT VALIDATED, indicates if the data has not been validated. Columns may vary depending the version of the quality flags in the series.