more user-friendly things

[adamwang15]

• combine sign_irf and zero_irf (0 for zero restriction, NA for no restrictions)
• allow inputs of matrices for restrictions on irf0 only (instead of arrays)
• rename sign_B
• progress bar
• specify_narrative function
• remove VB and other unnecessary parameters

[adamwang15]

this takes suspiciously long to run, try to make it faster

data(monetary)

# contractionary monetary policy shock
sign_irf       = matrix(NA, 6, 6)
sign_irf[, 1]  = c(NA, -1, -1, NA, -1, 1)
sign_irf       = array(sign_irf, dim = c(6, 6, 5))

# in October 1979 the shock
sign_narrative = rbind(c(1, 1, NA, 1, 166, 0),   # is positive
                       c(3, 1, 6,  1, 166, 0))   # greatest historical decomposition

specification  = specify_bsvarSIGN$new(monetary,
                                       p              = 12,
                                       sign_irf       = sign_irf,
                                       sign_narrative = sign_narrative)

posterior      = estimate(specification, S = 10)

• try to improve hd1_cpp