calibrateHarmDensity: Calibrate a harm density function
In uvic-cisur/cisurwac: CISUR's Wholly-Attributable Calibrators

Calibrate a harm density function

1	calibrateHarmDensity(count, popn, p_cd, pcc, gamma_relation, lb, ub, threshold)

`count`	Total number of events among the given population
`popn`	Total number of persons in the given population
`p_cd`	Proportion of given population that are current drinkers
`pcc`	daily per capita consumption in grams
`gamma_relation`	relationship between mean and standard deviation of the gamma distribution that governs alcohol consumption. By Kehoe, use 1.171 for male populations and 1.258 for female populations.
`lb`	lower bound of consumption
`ub`	upper bound of consumption
`threshold`	lower bound of consumption at which condition occurs