update.parsimonyCost compute the line vector of a parent node, given
the vectors of its daughters.
update.parsimonyCost(daughtersParams, ...)A line vector corresponding to the parent node.
a (ndaughters) x (nclus) matrix with the line vectors of the cost for the daughters node.
This function computes the cost of putting the parent in a state k, as the minimum number of shifts needed to get the given clustering of the trees bellow parental node.