a '>gtypes object with aligned sequences or a list of
aligned DNA sequences.
ignore.gaps
logical. Ignore gaps at a site when creating consensus.
If TRUE, then bases with a gap are removed before consensus is
calculated. If FALSE and a gap is present, then the result is a gap.
simplify
if there is a single locus, return result in a simplified
form? If FALSE a list will be returned wth one element per locus.