FindFMSY: Calculates yield at F, to be passed to optimizing function
In szuwalski/GeMS: Generic Management Strategy Evaluation

Calculates yield at F, to be passed to optimizing function

FindFMSY(x, MaxAge, VirInitN, VirInitS, vulnN, vulnS, NatMn, NatMs,
  matureN, matureS, WeightAtAgeN, WeightAtAgeS, steepnessN, steepnessS,
  RzeroN, RzeroS, LenAtAgeN, LenAtAgeS, sigmaRn, sigmaRs, RefYear,
  inputFs = 0, MovementN, MovementS)

`x`	Historical fishing mortality for nothern population
`MaxAge`	Maximum age
`VirInitN`	Initial biomass of northern population
`VirInitS`	Initial biomass of southern population
`vulnN`	Vulnerability matrix for northern population
`vulnS`	Vulnerability matrix for southern population
`NatMn`	Natural Mortality for northern population
`NatMs`	Natural Mortality for southern population
`matureN`	Proportions mature for northern population
`matureS`	Proportions mature for southern population
`WeightAtAgeN`	Weight-at-age matrix for northern population
`WeightAtAgeS`	Weight-at-age matrix for southern population
`steepnessN`	Steepness parameter for northern population
`steepnessS`	Steepness parameter for southern population
`RzeroN`	Virgin recruitment parameter for northern population
`RzeroS`	Virgin recruitment parameter for southern population
`LenAtAgeN`	Matrix of lengths at age for northern population
`LenAtAgeS`	Matrix of lengths at age for southern population
`sigmaRn`	Recruitment variability for northern population
`sigmaRs`	Recruitment variability for southern population
`RefYear`	Year of forecast
`inputFs`	Historical fishing mortality for southern population
`MovementN`	Proportion of emigration to the southern population
`MovementS`	Proportion of immigration into the northern population