Compute initial values for evolution error variance parameters under the dynamic horseshoe prior
initDHS(omega)List of relevant components: the T x p evolution error SD sigma_wt,
the T x p log-volatility ht, the p x 1 log-vol unconditional mean(s) dhs_mean,
the p x 1 log-vol AR(1) coefficient(s) dhs_phi,
the T x p log-vol innovation SD sigma_eta_t from the PG priors,
the p x 1 initial log-vol SD sigma_eta_0,
and the mean of log-vol means dhs_mean0 (relevant when p > 1)
T x p matrix of evolution errors