(list) state of the root, with:
random : random state (TRUE) or deterministic state (FALSE)
value.root : if deterministic, value of the character at the root
exp.root : if random, expectation of the character at the root
var.root : if random, variance of the character at the root
shifts
(list) position and values of the shifts :
edges : vector of the K id of edges where the shifts are
values : matrix p x K of values of the shifts on the edges (one column = one shift)
relativeTimes : vector of dimension K of relative time of the shift from the
parentnode of edges