compute_ev_price_disc: Compute economic value based on price change for discrete...
In pvrqualitasag/MeatValueIndex:

Economic value is computed based on price change between base distribution and a shifted distribution for a discrete trait.

1 2	compute_ev_price_disc(pn_mean, pn_sd, pvec_class_freq, pvec_threshold, pvec_price, pn_delta_mean, pn_gen_sd, pb_verbose = FALSE)

`pn_mean`	empirical population mean
`pn_sd`	empirical population standard deviation
`pvec_class_freq`	vector of empirical trait frequencies
`pvec_threshold`	vector of thresholds given by payment system
`pvec_price`	vector of prices given by payment system
`pn_delta_mean`	small change of population mean
`pn_gen_sd`	genetic standard deviation of trait
`pb_verbose`	level of output verbosity