ChooseSelect: Manually choose the historical selectivity pattern
Description
Input the first historical year, and all years where selectivity pattern
changed (separated by comma). Interactive plot which allows users to
specify a range for the length at 5% and full selection (LFS), as well as
selectivity at maximum length for each year. Produces a simple plot which
shows the range in selectivity pattern for each break-point year.
Selectivity-at-length is fixed in between break-point years. Note that this
function replaces 'nyears' in the Fleet object with the value defined here
(FstYr:current year).