solve_for_f: Function to solve for F by fleet based on catch for that year
In mcoshima/moMSE: Functions for Running a Management Strategy Evaluation

Function to solve for F by fleet based on catch for that year

1	solve_for_f(proj_catch, fleet, dat.list, year, N, total_catch = T)

`proj_catch`	the expected catch from fleet for the year (in numbers)
`fleet`	fleet you are calculating F for
`dat.list`	list including M, Nages, weight-at-age, and selectivity
`year`	year index
`N`	matrix of numbers-at-age, first column is year
`total_catch`	is the projected catch a combined catch (T) or only for that fleet (F)